CHAPTER 2: THE STRUCTURE OF ATOM

Transcription

1 CHAPTER 2: THE STRUCTURE OF ATOM A MATTER Learning Outcomes You should be able to: describe the particulate nature of matter, state the kinetic theory of matter, define atoms, molecules and ions, relate the change in the state of matter to the change in heat, relate the change in heat to the change in kinetic energy of particles, explain the inter-conversion of the states of matter in terms of kinetic theory of matter. Activity 1 Fill in the blanks with suitable word(s) in the box given Ions tiny molecules discrete smallest take part positively-charged in released atoms gas chemically solid absorbed different arrangement movement liquid 1. Matter is made up of. and particles. 2. The tiny particles may be atoms.. and. 3. An atom is the particle of an element that can.. in a chemical reaction. 4. A molecule is a group of two or more which are bonded together. 5. An ion is a. or negatively charged particle 6. Diffusion occurs when particles of a substance move between the particles of another substance. 7. Diffusion of matter occurs most rapidly in state, slower in.. state and slowest in.. state. This is due to the different and. of particles in the three states of matter. 8. Matter consists of small particles that always collide among each other. The particles move faster when energy is and the particles move slower when the energy is.... 1

2 Activity 2 1. Complete the table below. State of matter Solid Liquid Gas Draw the arrangement of particles The particles are The particles are The particles are packed.. Arrangement of together in an particles manner Particles can only Movement of and particles.. about their fixed positions Attractive forces Particles are attracted between the by very.. particles.. between the partcles Energy content of packed... apart from together but not in each other and in..... motion. Particles can Particles can...,.,. and and throughout the liquid.. freely Particles are held The attraction forces together by strong between particles are forces but... forces than the forces in solid (moderately) particles Underline the correct word in the passage below. When heat energy is supplied to particles in matter, its kinetic energy (increases /decreases) and the particles in matter vibrate ( faster/ slower). When matter loses heat energy, the kinetic energy of the particles (increases/decreases) and they vibrate ( faster/ slower). 3. State the change of matter for each conversion in the spaces provided. 2

3 A B... C.... D. E.. F 4. Complete the passage below by using the words given below. (solid, gas, boiling point, melting point, solid, gas, liquid, intermolecular, released, absorbed, overcome ) The temperature at which a completely changes to a liquid is called Boiling point is the temperature at which a changes into... During the boiling process, the temperature remains constant because the heat energy is by the particles and is used to... the forces between particles. 5. The graph below shows the change in temperature with time when a matter in solid state was heated. Temperature/ O C D B C A Time/s 3

4 Based on the graph above, complete the table below. Point States of matter Explanation in terms of energy change and movement of particles A to B Heating causes the particles to.. more energy and vibrate.. The temperature of the substance and the kinetic energy B to C Continuous heating does not cause the temperature of the substance to increase. The energy absorbed is used to the forces of attraction between the. The constant temperature is called the.... C to D Continuous heating causes the temperature of the liquid to The particles move because their kinetic energy.. 6. (a) The graph below shows the change in temperature with time when a matter in liquid state is left to cool. Temperature / O C P Q R Based on the graph above, complete the table below. S Time/s Point State of matter Explanation P to Q As cooling continues, particles lose their and move.. The temperature... Q to R The stronger bonds. during freezing release energy. This energy released is the same as the 4

5 energy. to the surroundings during cooling. Thus the temperature remains unchanged. This constant temperature is called.. R to S The is cooled. The particles vibrate. as the temperature. (b) Complete the passage below by using the words given below. (solid, gas, liquid, exactly balanced, decreased, increased) B Freezing point is the temperature at which a changes into During the freezing process, the temperature remains unchanged because the heat lost to the environment is... by the heat released when the liquid particles rearrange themselves to become solid. THE ATOMIC STRUCTURE Learning Outcomes You should be able to: describe the development of atomic model, state the main subatomic particles of an atom, compare and contrast the relative mass and the relative charge of the protons, electrons and neutrons, define proton number, define nucleon number, determine the proton number, determine the nucleon number, relate the proton number to the nucleon number, relate the proton number to the type of element, write the symbol of elements, determine the number of neutrons, protons and electrons from the proton number and the nucleon number and vice versa, construct the atomic structure. Activity 3 1. Complete the table and draw the structure of each atomic model. Model Structure Characteristic Dalton s atomic model proposed by in 1805 Thomson s atomic model proposed by.. in 1897 The atom was imagined as a small indivisible ball similar to a very tiny ball. J.J Thomson discovered.., a negatively-charged particle. The atom was described as a sphere of positive charge embedded with electrons. 5

6 Model Structure Characteristic Rutherford s atomic model proposed by in 1911 Ernest Rutherford discovered., a positively-charged particle in an atom. The central region of atom has a very small positively-charged.., which contains almost all the mass of the atom. Bohr s atomic model proposed by in 1913 Chadwick s atomic model proposed by... in 1932 The electrons in an atom move in.. around the nucleus which contains protons. Chadwick proved the existence of.., the neutral particle in the nucleus. The nucleus of the atom contains protons & neutrons, and the nucleus is surrounded by electrons. Activity 4 Fill in the blanks and complete the table. 1. Atoms are made up of subatomic particles namely protons, and.. 2. and.. are found in the nucleus of an atom while electrons surround the nucleus. 3. Subatomic particle Symbol Relative mass Relative electric charge Proton Neutron Electron 4. The proton number of an element is the number of in its atom. Proton Number, Z = Number Of Proton 5. Protons and neutrons are collectively called nucleons. The nucleon number of an element is the total number of.. and.. in its atom. 6

7 Nucleon Number, A = Number Of Proton + Number Of Neutron 6. The nucleon number is also known as the.. = Nucleon Number -- Proton Number = A -- Z 7. The standard representation for an atom of any element shows the proton number and the nucleon number of the element. It can be written as follows: A Z # A Nucleon number Z proton number X symbol of element X 1 H 1 3 Li 7 11 Na K 39 4 Be 9 12 Mg Ca Sc Sc 45 Proton number Nucleon number 5 B Al 27 6 C Si 28 7 N P 31 8 O S 32 9 F Cl 35 2 He 4 10 Ne Ar 40 By referring to part of the Periodic Table of Element above, complete the table below. Element Scandium Symbol Proton number No. of neutrons Nucleon number No. of electrons Standard representation Aluminium Argon Beryllium Boron Calcium Carbon Chlorine Fluorine 7

8 Helium Hydrogen Lithium Magnesium Neon Nitrogen Oxygen Phosphorus Potassium C ISOTOPES AND THEIR IMPORTANCE Learning Outcomes You should be able to: state the meaning of isotope, list examples of elements with isotopes, determine the number of subatomic particles of isotopes, justify the uses of isotope in daily life. Activity 5 Fill in the blanks. 1. Isotopes are atoms of the same element with the. of proton but.. of neutron. 2. Complete the table below: Element Number of isotopes Hydrogen 3 Oxygen 3 Carbon 3 Symbol of isotopes 1 H Number of protons 1 1 Number of electrons Number of neutrons Name of isotope 1 Hydrogen O 8 8 Oxygen O Carbon C 6 8 8

9 Chlorine 2 Bromine Cl Bromine Bromine For each of the isotope list below, state one of its uses. a) Gamma rays of Cobalt-60:. b). Carbon-14:.. c). Phosphorus-32:.. d). Sodium- 24: e). Iodine -131: D THE ELECTRONIC STRUCTURE OF AN ATOM Learning Outcomes You should be able to: describe electron arrangements of elements with proton numbers 1 to 20, draw electron arrangement of an atom in an element, state the meaning of valence electrons, determine the number of valence electrons from the electron arrangement of an atom. Activity 6 1. Electrons are filled in specific shells, starting with the shell nearest to the nucleus of the atom. Every shell can be filled only with a certain number of electrons. The first shell can be filled with a maximum of. electrons The second shell can be filled with a maximum of. electrons The third shell can be filled with a maximum of.electrons Use x as symbol for electrons. Draw the maximum number of electrons in each shell. 9

10 2(a) Draw the electron arrangement of a sodium atom, 23 11Na in the box and complete the table given. Number of protons Number of electrons Number of neutrons Proton number Nucleon number Electron arrangement (b) Draw the electron arrangement of a chlorine atom, Cl in the box and complete the table given. Number of protons Number of electrons Number of neutrons Proton number Nucleon number Electron arrangement x 3 Valence electrons are electrons in the.. shell of a neutral atom. 4 Identify the number of valence electrons in these atoms according to its electron arrangement. Atom of Element Electron Arrangement Number of valence electrons Oxygen 2.6 Aluminium Chlorine Neon 2.8 Potassium Magnesium

11 Carbon 2.4 Phosphorus Helium 2 11

12 CHAPTER 3 : CHEMICAL FORMULAE AND EQUATIONS A RELATIVE ATOMIC MASS (RAM) AND RELATIVE MOLECULAR MASS (RMM) Learning Outcomes You should be able to: state the meaning of relative atomic mass based on carbon-12 scale, state the meaning of relative molecular mass based on carbon-12 scale, state why carbon-12 is used as a standard for determining relative atomic mass and relative molecular mass, calculate the relative molecular mass of substances. Activity 1 (refer text book pg 28 ) Relative atomic mass of an element, A r = The average mass of an atom of the element 1/12 x the mass of an atom of carbon-12 Example: A r of C=12 A r of O=16 A r of Mg=24 1. The Relative atomic mass of an element is.... when compare with 1/12 of the mass of an atom of carbon Carbon-12 is chosen because it is a. and can be easily handled. 3. Find the relative atomic masses of these elements. Element Relative Atomic Mass Element Relative Atomic Mass Calcium, Ca Sodium, Na Iron, Fe Copper, Cu Carbon, C Hydrogen, H Potassium, K Lithium, Li Bromine, Br Activity 2 (refer text book pg 29 ) Argon, Ar Silver, Ag Caesium, Cs Lead, Pb Chlorine, Cl Flourine, F Aluminium, Al Zinc, Zn Helium, He Relative molecular mass of a substance, M r = The Average mass of a molecule of the substance 1/12 x the mass of an atom of carbon-12 12

13 Calculating Relative molecular mass,m r M r = The sum of A r of all atoms present in one molecule Example: Molecular formula 2 Hydrogen atoms M r of Water, H 2 O = 2(1) + 16 = 18 Relative atomic mass for Hydrogen Relative atomic mass for Oxygen M r of Carbon dioxide, CO 2 = (16) = 44 For ionic substance, Relative formula mass, F r = The sum of A r of all atoms present in the formula All A r, M r and F r have no unit Example: F r of Magnesium oxide, MgO = = 40 F r of Sodium chloride, NaCl = = The relative molecular mass of a molecule is when compared with 1/12 of the mass of one atom of 2. Calculate the relative molecular masses of the substances in the table below. Substance Molecular formula Relative molecular mass, M r Hydrogen gas H 2 2(1) = 2 Propane C 3 H 8 Ethanol C 2 H 5 OH Bromine gas Br 2 Methane CH 4 Glucose C 6 H 12 O 6 Ammonia NH 3 [Relative atomic mass : H,1; C,12; O,16; Br,80 ; N,14 ] 3. Calculate the relative formula masses of the following ionic compounds in the table. Substance Compound formula Relative formula mass, F r Potassium oxide K 2 O 2(39) + 16 = 94 Aluminium sulphate Al 2 (SO 4 ) 3 2(27)+3[32+4(16)]=342 Zinc nitrate Zn(NO 3 ) 2 13

14 Aluminium nitrate Al(NO 3 ) 3 Calcium carbonate CaCO 3 Calcium hydroxide Ca(OH) 2 Hydrated copper(ii) sulphate CuSO 4.5H 2 O (16) + 5[2(1) + 16]=250 Hydrated sodium carbonate Na 2 CO 3.10H 2 O Sodium hydrogen sulphate NaHSO 4 Aluminium chloride AlCl 3 Copper(II) sulphate CuSO 4 Zinc carbonate ZnCO 3 Potassium carbonate K 2 CO 3 [Relative atomic mass: O,16; C,12; H,1; K,39 ; Cu,64 ; Zn, 65; Cl, 35.5 ; Al, 27 S,32 ; Ca, 40; Na,23; N, 14] 14

15 B THE MOLE AND THE NUMBER OF PARTICLES Learning Outcomes You should be able to: define a mole as the amount of matter that contains as many particles as the number of atoms in 12 g of 12 C, state the meaning of Avogadro constant, relate the number of particles in one mole of a substance with the Avogadro constant, solve numerical problems to convert the number of moles to the number of particles of a given substance and vice versa. Activity 3 (refer text book pg 30 ) 1. To describe the amount of atoms, ions or molecules, mole is used. 2. A mole is an amount of substance that contains as many particles as the.... in exactly 12g of carbon A mole is an amount of substance which contains a constant number of particles atoms, ions, molecules which is 6.02 x The number 6.02 x is called (N A ) 5. In other words: 1 mol of atomic substance contains. atoms 1 mol of molecular substance contains. molecules 1 mol of ionic substance contains.. formula units 6. Relationship between number of moles and number of particles (atom/ion/molecules): number of moles x Avogadro Constant number of particles A vogadro Constant Number of moles Number of particles 0.5 mol of carbon atoms atoms of carbon 15

16 0.2 moles of hydrogen gas ( H 2 ) (i)..molecules of hydrogen gas (ii).atoms of hydrogen 2 mol of carbon dioxide molecules x molecules of carbon dioxide gas contains :. atoms of C and. atoms of O mol of calcium ions calcium ions. mol of water 6.02 x molecules of water 0.4 mol of ozone gas ( O 3 ).x molecules of ozone, contains : atoms of Oxygen. 7. Complete these sentences. a) 1 mol of calcium contains.. atoms b) 2 mol of iron contains.. atoms c) 2 mol of magnesium oxide, (MgO) contains ions d) 2 mol of sodium carbonate, (Na 2 CO 3 ) contains. e) 3 mol of carbon dioxide, (CO 2 ) contains.. molecules f) 0.5 mol Copper (II) nitrate, Cu(NO 3 ) 2 contains. Cu 2+ ions and. NO - 3 ions 16

17 C NUMBER OF MOLES AND MASS OF SUBSTANCES Learning Outcomes You should be able to: state the meaning of molar mass, relate molar mass to the Avogadro constant, relate molar mass of a substance to its relative atomic mass or relative molecular mass, solve numerical problems to convert the number of moles of a given substance to its mass and vice versa. Activity 4 (refer text book pg 33 ) 1. The molar mass of a substance = The molar mass of mole of the substance. = The mass of (N A ) number of particles = The mass of particles Number of moles x Molar mass Mass in g 2. Calculating the Mass from a number of Moles Therefore : Number of moles =. mass of the substance. Mass of 1 mole of the substance Mass of substance = Number of moles x Mass of 1 mole Example 1 : What is the mass of 2 moles of carbon? Mass = 2 x 12 = 24g Example 2 : What is the mass of 2 moles of H 2 O? Mass = 2 x [ 2(1) + 16 ] = 36g 17

18 3. Calculate the masses of these substances a) 2 moles of aluminium atoms Mass = b) 10 moles of iodine atoms Mass = c) 3 moles of lithium atoms Mass = d) 0.5 moles of oxygen gas (O 2 ) Mass = e) 0.1 moles of sodium Mass = f) 2 moles of chlorine molecules (Cl 2 ) Mass = g) 1 mole of carbon dioxide ( CO 2 ) Mass = h) 3 moles of nitric acid, ( HNO 3 ) Mass = i) 2 moles of calcium carbonate (CaCO 3 ) Mass = j) 0.25 moles of calcium chloride (CaCl 2 ) Mass = k) 0.25 moles of sodium hydroxide (NaOH) Mass = m) 0.5 moles of potassium manganate (VII) (KMnO 4 ) Mass = l) 0.25 moles of sodium carbonate (Na 2 CO 3 ) Mass = n) 0.25 moles of hydrated magnesium sulphate (MgSO 4.7H 2 O) Mass = Activity 5 4. Calculate the Number of Moles from a given Mass Example : How many moles are there in 88g of CO 2 Number of moles = = 2 moles a) 2g of helium atoms Number of moles = b) 6g of carbon atoms Number of moles = 18

19 c) 16g of helium atoms Number of moles = d) 4g of sulphur atoms Number of moles = e) 4g of oxygen molecules (O 2 ) Number of moles = f) 213g of chlorine molecules (Cl 2 ) Number of moles = g) 0.56g of nitrogen molecules (N 2 ) Number of moles = h) 254g of iodine molecules (I 2 ) Number of moles = i) 88g of carbon dioxide (CO 2 ) Number of moles = j) 3.1g of sulphur dioxide (SO 2 ) Number of moles = k) 560g of potassium hydroxide (KOH) Number of moles = l) 392g of sulphuric acid (H 2 SO 4 ) Number of moles = m) 170g of ammonia (NH 3 ) Number of moles = n) 120g of magnesium oxide (MgO) Number of moles = o) 4g of sodium hydroxide (NaOH) Number of moles = p) 73g of hydrogen choride (HCl) Number of moles = q) 15.8g of potassium manganate (VII) KMnO 4 Number of moles = r) 8g of ammonium nitrate (NH 4 NO 3 ) Number of moles = s) 0.78g of aluminium hydroxide Al(OH) 3 Number of moles = t) 0.92g of ethanol (C 2 H 5 OH) Number of moles = 19

20 Activity 6 5. Complete the following table. Element/compound Chemical formulae Molar mass Calculate Copper Cu RAM= 64 (a)mass of 1 mol = g (b) Mass of 2 mol =. g (c)mass of ½ mol =.g (d)mass of 3.01x10 23 Cu atoms = Sodium hydroxide NaOH RFM= 40 (a) Mass of 3 mol of sodium hydroxide = (b) Number of moles of sodium hydroxide in 20 g = Zinc nitrate Zn(NO 3 ) 2 RFM = a) Number of moles in 37.8 g of zinc nitrate : D NUMBER OF MOLES AND VOLUME OF GAS Learning Outcomes You should be able to: state the meaning of molar volume of a gas, relate molar volume of a gas to the Avogadro constant, make generalization on the molar volume of a gas at a given temperature and pressure, calculate the volume of gases at STP or room conditions from the number of moles and vice versa, solve numerical problems involving number of particles, number of moles, mass of substances and volume of gases at STP or room conditions. Activity 7 (refer text book pg 36, 37 ) 1. The molar volume of a gas is defined as the. 20

21 2. One mole of any gas always has the under the same temperature and pressure. 3. The molar volume of any gas is 24 dm 3 at or 22.4 dm 3 at. Example : 1 mol of oxygen gas, 1 mol of ammonia gas, 1 mol helium gas and 1 mol sulphur dioxide gas occupies the same volume of 24 dm 3 at room condition Number x 22.4/24 dm 3 of moles of gas 22.4/24 dm 3 x 22.4 / 24 dm 3 Volume of gas 4. Calculate the volume of gas in the following numbers of moles at STP Example : Find the volume of 1 mole of CO 2 gas Volume = number of moles x 22.4 dm 3 = 1 x 22.4 dm 3 = 22.4 dm 3 a) 3 moles of oxygen Volume = b) 2 moles of CH 4 Volume = c) 0.3 moles of Argon Volume = d) 0.2 moles of SO 3 Volume = e) 0.1 moles of N 2 Volume = f) 1.5 mol of N 2 Volume = 21

22 5. Complete the diagram below. (Refer to Page 33,34 & 38-Chemistry textbook) Volume of gas (dm 3 ) Mass in gram Number of moles No of particles Activity 8 Solve these numerical problems 1. What is the volume of 0.3 mole of sulphur dioxide gas at STP? [Molar volume: 22.4 dm 3 mol -1 at STP] (Ans: 6.72 dm 3 ) 2. Find the number of moles of oxygen gas contained in a sample of 120 cm 3 of the gas at room conditions. [Molar volume: 24 dm 3 mol -1 at room conditions] (Ans: mol) 3. Calculate the number of water molecules in 90 g of water, H 2 O. [Relative atomic mass: H, 1; O, 16. Avogadro constant, N A : 6.02 x mol -1 ] (Ans; 3.01x molecules) 22

23 4. What is the volume of 24 g methane,ch 4 at STP? [Relative atomic mass: H, 1; C, 12. Molar volume: 22.4 dm 3 mol -1 at STP] (Ans: 33.6 dm 3 ) 5. How many aluminium ions are there in 20.4 g of aluminium oxide, Al 2 O 3? [Relative atomic mass: O, 16; Al, 27. Avogadro constant, N A : 6.02 x mol - (2 x 0.2 x 6.02 x10 23 ) 6. Calculate the number of hydrogen molecules contained in 6 dm 3 of hydrogen gas at room conditions. [Molar volume: 24 dm 3 mol -1 at room conditions Avogadro constant, N A : 6.02 x mol -1 ] (Ans: 1.505x10 23 molecules) 7. Find the volume of nitrogen in cm 3 at STP that consists of x nitrogen molecules. [Molar volume: 22.4 dm 3 mol -1 at STP. Avogadro constant, N A : 6.02 x mol -1 ] (Ans: 8.96 dm 3 ) 23

24 E CHEMICAL FORMULAE Learning Outcomes You should be able to state the meaning of chemical formula state the meaning of empirical formula state the meaning of molecular formula determine empirical and molecular formula of substances compare and contrast empirical formula with molecular formula solve numerical problems involving empirical and molecular formula. write ionic formula of ions construct chemical formulaf ionic compounds state names of chemical compounds using IUPAC nomenclature. use symbols and chemical formula for easy and systematic communication in the field of chemistry. ACTIVITY 9 (Refer text book pg 40) 1) A Chemical formula - A representation of a chemical substance using letters for and subscripts to show the numbers of each type of.. that are present in the substance. The letter H shows.. H 2 Subscript shows 2 hidrogen atoms in a molecule 2) Complete this table Chemical subtance Chemical formulae Notes Water.. 2 atoms of H combine with 1 atom of O.. NH 3. atoms of H combine with 1 atom of N Propane C 3 H 8.. atoms of C combine with. atoms of H Magnesium oxide..... H 2 SO 4 24

25 3). There are two types of chemical formulae. Complete the following: ** Empirical Formula The simplest.. ratio of atoms of each in the compound. ** Molecular Formula The actual of atoms of each that are present in a molecule of the compound Remember: Molecular formula = (Empirical formula) n Example: (i) Compound Ethene (ii) Compound Glucose Molecular formula - C 2H 4 Molecular formula - C 6H12O6 Empirical formula -... Empirical formula -... Activity 10 1 Find the empirical formula of a compound Example of calculation: a) When g of metal X oxide is reduced by hydrogen, g of metal X is produced. Find the empirical formula of metal X oxide [ RAM; X,207; O,16 ] Element X O Mass of element(g) Number of moles of ( ) 16 atoms Ratio of moles Simplest ratio of moles Empirical formula : b) A certain compound contains the following composition: Na 15.23%, Br 52.98%, O 31.79%, [ RAM : O, 16; Na, 23; Br,80] (Assume that 100g of substance is used) Element Na Br O Mass of element(g) Number of moles atoms Ratio of moles Simplest ratio of moles 25

26 Empirical formula::. c) Complete the table below. Compound Molecular Formula Empirical formula Value of n Water H 2 O Carbon Dioxide CO 2 CO 2 Sulphuric Acid H 2 SO 4 Ethene C 2 H 4 CH 2 Benzene C 6 H 6 Glucose C 6 H 12 O 6 d) 2.52g of a hydrocarbon contains 2.16 g of carbon. The relative molecular mass of the hydrocarbon is 84. [RAM H,1; C,12] i. Find the empirical formula of the hydrocarbon ii. Find the molecular formula of the carbon. Activity 11 Complete the table below : :Chemical Formula for ionic compounds: Cation Formula Anion Formula Hydrogen ion Lithium ion H Flouride ion F Chloride ion Sodium ion Potassium ion Magnesium ion Calcium ion Bromide ion Iodide ion Hydroxide ion 2 Ca Nitrate ion 26

27 Barium ion 2 Ba Manganate(VII) ion Copper(II) ion Ethanoate ion CH 3 COO Iron(II) ion Iron (III) ion Sulphate ion 2 O Lead (II) ion Sulphide ion 2 S Zinc ion Carbonate ion Chromium (III) ion Dichromate (VI) ion Cr 2 2 O 7 Aluminium ion Ammonium ion 3 Al Chromate (VI) ion 3 PO 4 Avtivity 12 a) Chemical formula of an ionic compound comprising of the ions X m+ and Y n- is constructed by exchanging the charges of each element. The formula obtained will X n Y m Example : Sodium oxide Copper (II) nitrate Na + O 2- Cu 2+ NO = Na 2 O =... b) Construct a chemical formula for each of the following ionic compounds: (i) Magnesium chloride (ii) Potassium carbonate (iii) Calcium sulphate (iv) Copper (II) oxide (v) Silver nitrate (vi) Zinc nitrate 27

28 (vii) Aluminium oxide (viii) Iron(II) hydroxide (ix) Lead(II) sulphide (x) Chromium(III) sulphate CHEMICAL EQUATIONS Learning Outcomes You should be able to 1. state the meaning of chemical equation identify the reactants and products of a chemical equation 2. write and balance chemical equations 3. interpret chemical equations quantitatively and qualitatively 4. solve numerical problems using chemical equations 5. identify positive scientific attitudes and values practiced by scientist in doing research 6. justify the need to practice positive scientific attitudes and good values in doing researsh 7. use chemical equations for easy and systematic communication in the field of chemistry. Activity 13 (refer text book pg 48) Example: C (s) + O 2 (g) CO 2 (g) Reactant 1) Qualitative aspect of chemical equation: product a) Arrow in the equation the way the reaction is occurring b) Substances on the left-hand side.. c) Substances on the right-hand side d) State of each substance : (s), (l), gas.and aqueous solution. 2) Quantitative aspect of chemical equations Coefficients in a balanced equation the exact proportions of reactants and products in equation. Example: 2 H 2 (g) + O 2 (g) 2 H 2 O (Interpreting): 2 molecules (2 mol) of H 2 react with 1 molecule (1 mol) of O2 to produced 2 molecules(2 mol) of water (l) 28

29 Complete the following word equations and write in chemical equation a) Sodium + chlorine.. + NaCl b) Carbon +.. Carbon dioxide. +.. c) Sulphur + oxygen d) Zinc + oxygen.. + O 2.. 3) Write a balanced equation for each of the following reactions and interpret the equations quantitatively. (a). Carbon monoxide gas + oxygen gas carbon dioxide gas Interpreting: (b). Hydrogen gas + nitrogen gas ammonia gas. Interpreting:.. (c). Aluminium + Iron (III) oxide aluminium oxide + Iron. Interpreting:. Activity 14 ** Numerical Problems Involving Chemical Equations Hydrogen peroxide decomposes according to the following equation: 2 H 2O2 (l) 2 H 2 O (l) + O 2 (g) 1). Calculate the volume of oxygen gas, O 2 measured at STP that can be obtained from the decomposition of 34 g of hydrogen peroxide, H 2O2. [Relative atomic mass : H, 1 ; O, 16. Molar volume : dm 1 mol at STP] 29

30 2).Silver carbonate Ag 2 CO 3 breaks down easily when heated to produce silver metal 2 Ag 2 CO 3 (l) 4 Ag (s) + 2 CO 2 (g) + O 2 Find the mass of silver carbonate that is required to produce 10 g of silver [Relative atomic mass: C, 12 ; O, 16 ; Ag, 108] (Ans: 11.2 dm 3 ) (Ans : 12.77g) 3). 16 g of copper (II) oxide, CuO is reacted with excess methane, CH 4. Using the equation below, find the mass of copper that is produced. [Relative atomic mass : Cu, 64 ; O, 16] 4 CuO (s) + CH 4 (g) 4 Cu (s) + CO 2 (g) + 2 H 2 O (l) (Ans : 12.8 g) 30

31 4). A student heats 20 g of calcium carbonate CaCO 3 strongly. It decomposes according to the equation below: CaCO 3 (s) CaO (s) + CO 2 (g). (a). If the carbon dioxide produced is collected at room conditions, what is its volume? (b). Calculate the mass of calcium oxide, CaO produced. [Relative atomic mass: C, 12 ; O, 16; Ca, 40. Molar volume : 24 dm 3 mol 1 at room conditions] (Ans : (a). 4.8 dm 3 (b) 11.2 g) 31

32 CHAPTER 4 :PERIODIC TABLE OF ELEMENTS A ANALYSING THE PERIODIC TABLE OF ELEMENTS Learning Outcomes You should be able to: describe the contributions of scientists in the historical development of the Periodic Table, identify groups and periods in the Periodic Table, state the basic principle of arranging the elements in the Periodic Table from their proton numbers, relate the electron arrangement of an element to its group and period, explain the advantages of grouping elements in the Periodic Table, predict the group and the period of an element based on its electron arrangement. Activity 1 Draw lines to match name of scientist with their contribution Name of Scientist Lothar Meyer Henry J. G. Moseley Antoine Lavoisier John Newlands Johann W. Dobereiner Dimitri Mendeleev Contribution First scientist to classify substances Classified the elements into group of three with similar chemical properties Arranged the known elements in order of increasing atomic mass. Elements with similar properties recurred at every eighth element. Plotted a graph of the atomic volume against the atomic mass of elements Left gaps in the table to be filled by undiscovered elements Rearranging the elements in order of increasing proton number Activity 2 1 Arrangement of elements in the Periodic Table a) Elements are arranged in an increasing order of b) Each vertical column is called a.. c) Each horizontal rows is called. d) Elements with similar chemical properties are placed in the same 32

33 2. Complete the table below. Element Electron arrangement Number of valence electrons Group Number of shells occupied with electrons Period 1 1 H 4 2 He Li B C N O 19 9 F Ne Mg Al Si S Cl K Ca

34 3. An atom of element E has 10 neutrons. The nucleon number of element E is 19. In which group and period is element E located in the Periodic Table? Answer :Group Period 4. An atom of element G has 3 shells occupied with electrons. It is placed in group 17 of the Periodic Table. What is the electron arrangement of atom G? Answer : Electron arrangement of atom G B ANALYSING GROUP 18 ELEMENTS Learning Outcomes: You should be able to: list all Group 18 elements, state in general the physical properties of Group 18 elements, describe the changes in the physical properties of Group 18 elements, describe the inert nature of elements of Group 18, relate the inert nature of Group 18 elements to their electron arrangements, relate the duplet and octet electron arrangements of Group 18 elements to their stability, describe uses of Group 18 elements in daily life.. Activity 3 : Analysing Group 18 Elements 1 Physical Properties of Group 18 Elements [Circle the correct answer]. Down the Group : a) Atomic radius /Atomic size increase/ decrease b) Melting point and Boiling point increase/ decrease c) Density increase/ decrease 2 Complete the figure below by giving the uses of Group 18. * Krypton * Xenon * Helium * Radon Uses of Group 18 * Neon * Argon 3 All noble gases are. which means chemically unreactive. This is because they have. electron arrangement. 34

35 Example : (i) Helium atom has. valence electrons which is called a electron arrangement (ii) Other noble gases has valence electrons which is called an. electron arrangement. 4.The noble gases exists as. gases because their electron arrangement are very.. C ANALYSING GROUP 1 ELEMENTS Learning Outcomes You should be able to: list all Group 1 elements. state the general physical properties of lithium, sodium and potassium, describe changes in the physical properties from lithium to potassium, list the chemical properties of lithium, sodium and potassium, describe the similarities in chemical properties of lithium, sodium and potassium, relate the chemical properties of Group 1 elements to their electron arrangements, describe changes in reactivity of Group 1 elements down the group, predict physical and chemical properties of other elements in Group 1 Activity 4 A State 3 physical properties of group 1 elements. a) b) c) B Chemical Properties of Group 1 Elements (Alkali metals ) 1. Group 1 elements react vigorously with water to produce alkaline metal hydroxide solutions and hydrogen gas Example: 2 Li + 2H 2 O 2 LiOH + H 2 Write down the balanced equation when potassium reacts with water.. 2. Group 1 elements react with oxygen gas rapidly to produce white solid metal oxides. Example: 4 Li + O2 2 Li 2 O Write down the balanced equation when rubidium reacts with oxygen 3. Group 1 elements react t with chlorine gas Cl 2, to form white solid metal chlorides. Example: 2 Na + Cl2 2 NaCl Write down the balanced equation when potassium reacts with chlorine gas.. 35

36 4 The reactivity of Group 1 elements increases when going down the group. Explain why. a) When going down Group 1 the single valence electron in the outermost occupied shell become.. from the nucleus. b) The attraction between the nucleus and the valence electron become.. c) Therefore it is. for the atom to donate the single valence electron to achieve the stable electron arrangement. 5 Potassium reacts more vigorously with water as compared to sodium. Explain. (Proton number: Na, 11 ; K, 19) Activity 5 Complete the table below and answer the following questions : Alkali Metal Proton number Number of electrons Electron arrangement Lithium 3 Sodium 11 Potassium 19 Rubidium Caesium Number of valence electrons 1) Lithium, sodium and potassium have similar chemical properties because their atoms have. electron in their outermost occupied shell. 2) How an atom of alkali metal achieve a stable electron arrangement of inert gas? 3) What is the charge of an alkali metal ion?.... 4) Reactivity of alkali metals increases from Lithium to Caesium. Explain why. 36

37 Activity 6 To Investigate The Chemical Properties of Lithium, Sodium & Potassium 1) The Reaction of alkali metals with water, H 2 O Problem Statement: How does the reactivity of Group 1 elements change when they react with water? Hypothesis: their reactions Variables: When going down Group 1, alkali metals become more reactive in with water. Manipulated variable Different types of alkali metals Responding variable Reactivity of metals with water Fixed variables water, size of metals alkali metal water a) Write the procedure to carry out this experiment. (refer to practical book pg 39) b) Complete this table (Data & Observation ) Alkali metal Observation Lithium Sodium Potassium 2) The Reaction of alkali metals With Oxygen, O 2 (This procedure can also be used to test the reaction of alkali metals with chlorine gas!) a) Problem Statement: b) Hypothesis: c) Variables: Manipulated variable 37

38 Responding variable. Fixed variables... Alkali metal oxygen d) Write the procedure of this experiment. (refer to practical book pg 36) e) Data & Observation Alkali metal Lithium Observation Sodium Potassium f) Based on your results, arrange the alkali metals in ascending order of reactivity. 38

39 D ANALYSING GROUP 17 ELEMENTS Learning Outcomes You should be able to: list all Group 17 elements, state the general physical properties of chlorine, bromine and iodine, describe changes in the physical properties from chlorine to iodine, list the chemical properties of chlorine, bromine and iodine, describe the similarities in chemical properties of chlorine, bromine and iodine, describe changes in reactivity of Group 17 elements down the group, predict physical and chemical properties of other elements in Group 17,. Activity 7 1) State the uses of Chlorine and iodine a) Chlorine. b) Iodine.. 2) (a) Give the physical state of halogens below at room temperature : i) Fluorine: ii) Chlorine: iii) Bromine: iv) Iodine :. (b) Fill in the blanks below. Cl 2 melting and colour of Density Br 2 boiling points halogens. I 2.. becomes. 3) When going down the Group 17, the melting and boiling points increase. Explain 4) Chemical Properties of Group 17 Elements a) Group 17 elements react with water to form two acids Example: Cl 2 + H 2 O HCl + HOCl Hydrochloric acid hypochlorus acid Write a balanced equation when bromine reacts with water. 39

40 b). In gaseous state they react with hot iron to form a brown solid, iron (III) halides. Example: 2 Fe + 3Br 2 2FeBr 3 Write a balanced equation when iodine vapour reacts with iron c). Group 17 elements react t with sodium hydroxide solution, NaOH, to form sodium halide, sodium halate (I) and water Example: I NaOH NaI + NaOI + H 2 O Write a balanced equation when chlorine reacts with sodium hydroxide solution 5)The reactivity of Group 17 elements decreases when going down the group. Explain why. a) When going down the Group 17 atomic size.. b) The outermost occupied shell becomes. from the nucleus. c) Therefore the strength to attract one electron into the outermost occupied shell by the nucleus becomes 6) Chlorine gas reacts more vigorously with hot iron as compared to bromine gas. Explain (Proton number: Cl, 17 ; Br, 35) Activity 8 To investigate the Chemical properties of Group 17 elements. The Reaction of halogens with iron (refer practical book pg 44) 1) Data and Observation (Complete the following table) Reactant Water Halogen Observation Chlorine Bromine Iodine Iron wool Sodium hydroxide, NaOH solution 40

41 2) Based on your results, arrange the halogens, Cl 2, Br 2, I 2 in ascending order of reactivity. 3) Element E is placed below element D in Group 17 of the Periodic Table. (a) Compare the melting and boiling points of element D with element E. Explain your answer. (b) Write a chemical equation for the reaction between element D and hot iron. E ANALYSING ELEMENTS IN A PERIOD Learning Outcomes You should be able to: list all elements in Period 3, write electron arrangements of all elements in Period 3, describe changes in the properties of elements across Period 3, state changes in the properties of the oxides of elements across Period 3, predict changes in the properties of elements across Period 2, Activity 9 Period 3 in the Periodic Table Properties of Elements 1) Complete the table and answer the question given below Element Na Mg Al Si P S Cl Ar Proton number Electron arrangement Number of valence electrons Atomic radius (pm) Physical state at Solid Solid Solid Solid Solid Solid Gas Gas room temperature Electronegativity

42 2) Fill in the blanks with the correct answer. a). The proton number.. by one unit from one element to the next element b) All the atoms of elements have.. shells occupied with electrons. c) The number of valence electrons in each atom. from 1 to 8. d) The physical state at room temperature changes from.. to e) The atomic radius (atomic size) of elements from left to right across the period 3 f) The electronegativity of elements... from left to right across the period 3. Activity 10 1) Below are some oxides of elements of Period 3. *Sodium oxide, Na 2 O *Silicon (IV) oxide, SiO 2 *Aluminium oxide, Al 2O3 *Sulphur dioxide, SO 2 (a) Which of these oxides can react with (i) (ii) dilute nitric acid? sodium hydroxide solution? (b) Based on your answers in (a), what inferences can you make about the properties of each of the oxides? (Acidic/Basic/Amphoteric) Oxides Oxides properties Sodium oxide Magnesium oxide Aluminium oxide Silicon (IV) oxide Phosphorus (V) oxide Sulphur dioxide 2) 7 3 Li, C, 9 F The diagram above shows the symbols of lithium, carbon and fluorine. (a) Which period in the Periodic Table can you find the three elements? Explain. 42

43 (b) Arrange the three elements in order of increasing atomic size. (c) Compare the electronegativity of the three elements. Explain your answer. The electronegativity of the elements (i) from Li, C, F This is due to the (ii).. nuclei attraction on the valence electrons and the (iii) in atomic size. F TRANSITION ELEMENTS Learning Outcomes You should be able to: identify the positions of transition elements in the Periodic Table, give examples of transition elements, describe properties of transition elements, state uses of transition elements in industries. Activity 11 1 (a) Transtition elements are elements from Group...to Group (b) State 3 examples of transtition elements found in Period Complete the diagram below. Special characteristics of Transition elements 3 Transition elements and their compounds are useful catalysts. Complete the table below Chemical Process Product Catalysts Haber Ostwald Contact 43

44 4 Transition elements form coloured ions or compound. Complete the table below Ion of transition element Formula of the ion Colour of aqueous solution Cooper (II) ion Iron (II) ion Iron (III) ion Chromium (III) ion Chromate (VI) ion Dichromate (VI) ion Manganese (II) ion Manganate (VI) ion Fe 2+ Yellowish Brown 4 Transition elements form ions with different Oxidation Numbers. Elements Compound Chemical Formula Oxidation Number Manganese Manganese (II) chloride Manganese (IV) oxide Iron Copper Potassium manganate (VI) Iron (II) chloride Iron (III) chloride Copper (I) chloride Copper (II) oxide **(Precious stones such as emerald, rubies, sapphire and jade are beautiful due to the colours of the transition element compounds present in them ) 44

45 Activity 12 1 Diagram 1 shows part of the Periodic Table of the Elements. D, E, G, L, M, and J, that do not represent the actual symbol of the element D E G L M J Diagram 1 Using the letters in the Periodic Table of the Elements in Diagram 1, answer the following questions. (a) (i) State the position of element E in the Periodic Table.. (ii) Choose the element which exhibit different oxidation numbers in its compounds (b) Element D combines with element L to form a compound. Write the chemical formula of this compound (c) D and E have the same chemical properties (i) Which element is more reactive?... (ii) Explain your answer in (c) (i)... (d) Which element exists as diatomic molecules?

46 2 The information shows the chemical symbols which represent elements W, X, Y and Z W X Y Z (a) State three subatomic particles in an atom (b) (i) What is the meaning of the period in the Periodic Table of element?... (ii) State the period of element W in the Periodic Table of element. Explain (c) (i) Compare the atomic size of element W and X.... (ii) Explain your answer in (c) (i)

47 CHAPTER 5 : CHEMICAL BONDS A Formation of Compounds Learning Outcomes: You should be able: explain the stability of noble gases explain the conditions for the formation of chemical bonds state the types of chemical bonds Activity 1: Formation of chemical bonds Choose the correct answer from the table Sharing ionic stable chemical bonds monoatomic arrangement inert covalent duplet 1 Noble gases are gases. They exist as.. gases and are chemically unreactive. They have... octet or.. electron.. 2 Other atoms besides noble gases tend to achieve the stable electron arrangement through the formation of 3 Two types of chemical bonds : (i) (ii).. bond - formed when atoms join together by transferring of electrons.. bond - formed when atoms join together by..of electrons B IONIC BONDS Learning outcomes: You should be able to: explain the formation of ions write the electron arrangements for the ions formed explain the formation of ionic bonds illustrate electron arrangement of an ionic bond illustrate the formation of ionic bonds Activity 2 : Formation of ions 1 Underline the correct answer. To achieve a stable electron arrangement : (i) A metal atom (donates / accepts) electrons, forming a (positive / negative) ion (ii) called cation. A (non-metal / metal) atom accepts electrons, forming a (positive / negative) ion 47

48 called anion. 2 Complete the diagram below. (a) (b) (Refer to page F4 Chemistry text book) Activity 3 : Formation of ionic bonds Fill in the blanks with the correct words. 1 Formation of ionic compound, sodium chloride ( NaCl ) 48

49 Electron arrangement of sodium atom is... A sodium atom.one electron to achieve the electron arrangement which is 2.8. Sodium ion,..... is formed Electron arrangement of chlorine atom is.. Electron from sodium atom is transferred to a. atom A chlorine atom electron from sodium atom to.. the stable electron which is Chloride ion,.. is formed The sodium ion, Na and chloride ion, to form an ionic compound.., NaCl. Cl formed are..to one another The strong.forces between the opposite-charged ions is called.bond. (Refer to page 86 - F4 Chemistry text book) 2 Complete the diagram below Sodium atom,na Chlorine atom,cl Sodium ion, Chloride ion,.. 3 (a) Fill in the blanks with the correct answers. Formation of ionic compound magnesium chloride, MgCl 2. Electron arrangement of magnesium atom is... A magnesium atom.two electrons to achieve the electron arrangement which is, 2.8. Magnesium ion,..... is formed Electron arrangement of chlorine atom is Electrons from magnesium atom is transferred to two. atoms A chlorine atom electron from magnesium atom to.. the stable electron which is Chloride ion,.. is formed 49

50 The magnesium ion,mg 2+ and two chloride ions, Cl formed are to one another to form an ionic compound., MgCl 2 The strong.forces between the opposite-charged ions is called..bond (Refer to page 86 - F4 Chemistry text book) (b) Complete the diagram below. (Refer to page 86 - F4 Chemistry text book) C Covalent Bonds Learning Outcomes: You should be able : state the meaning of covalent bonds explain the formation of covalent bonds illustrate the formation of covalent bonds compare and contrast the formation of ionic and covalent bonds Activity 4 : Formation of covalent bonds Fill in the blanks with the correct words. 1 Covalent bonds are formed when.. atoms.. electrons to achieve. electron arrangements. 2 Types of covalent bonds:- (i) (ii) (iii) 3 A single bond is formed when of electrons is shared between two atoms. A double bond is formed when..of electrons is shared between two atoms. A triple bond is formed when.of electrons is shared between two atoms. 4 Formation of hydrogen molecules, H 2 :- 50

51 A hydrogen atom has valence electron, with an electron arrangement of... It needs.. more electron to achieve the.. electron arrangement..hydrogen atoms one electron each for Shared-paired electrons forms a.. bond in the hydrogen molecule, H 2 Single bond holds the two hydrogen atoms together because the shared-pair of electrons is attracted to the.. of both atoms 5 Complete the diagram below. (a) (b) A covalent bond can be illustrated by using. Activity 5 : Formation of covalent bonds 1 Formation of oxygen molecules, O 2 : An oxygen atom has valence electron, with an electron arrangement of.. It needs.more electrons to achieve the.. electron arrangement...oxygen atoms share pairs of electrons forming a.. bond 2 (a) Draw the electron arrangement for the formation of oxygen molecule. [Proton number : O, 8 ;] (b) Illustrate the formation of oxygen molecule using the Lewis structure. 51

52 3 Formation of a nitrogen molecule, N 2 : A nitrogen atom has valence electron, with an electron arrangement.... It needs more electrons to achieve the.. electron arrangement..nitrogen atoms share pairs of electrons forming a covalent bond 4 Draw the electron arrangement for the formation of nitrogen molecule. [Proton number : N, 7] (b) Illustrate the formation for nitrogen molecule using the Lewis structure. Activity 6 1 Draw the electron arrangements for the formation of the following ionic compounds: [Proton number : Li, 3 ; Ca, 20 ; O, 8 ; Cl, 17 ] (a) Lithium oxide, Li 2 O (b) Calcium chloride, CaCl 2 52

53 2 Draw the electron arrangements for the formation of the following covalent compounds [Proton number : C, 6 ; Cl, 17, : O, 8] (a) Tetrachloromethane, CCl 4 (b) Carbon dioxide molecule, CO 2 3 Complete the table below to compare the characteristics for the formation of ionic and covalent bonds. Ionic bond Characteristic Covalent bond Valence electrons Electrons involved Electron transfer to achieve stable electron arrangement Elements Bond formation Particles Non-metals atom and non metal atoms D PROPERTIES OF IONIC AND COVALENT BONDING Learning outcomes You should be able to: list the properties of ionic compounds. list the properties of covalent compounds explain the differences in the electrical conductivity of ionic and covalent compounds describe the differences in melting and boiling points of ionic and covalent compounds compare and contrast the solubility of ionic and covalent compounds state the uses of covalent compounds as solvents. Activity 7 : Physical properties of ionic and covalent compounds 1. Complete the table of the properties of ionic and covalent compounds, using the words given in the box : conduct electricity in aqueous solution or molten state do not conduct electricity low solid high insoluble soluble solid, liquid, gas 53

54 Ionic compound Properties Covalent compound Physical states at room temperature Melting points Boiling points Electrical Conductivity Solubility in water Solubility in organic solvent 2 Explain why ionic compounds are able to conduct electricity in aqueous solution or in molten state but not in solid state Explain why covalent compound do not conduct electricity in all states... 4 Explain why ionic compounds have higher melting points than covalent compounds... 5 Example of covalent compounds ;-... Uses of covalent compounds as solvent in our daily lives:... (Refer to page F4 Chemistry text book) Activity 8 1 Atom A Atom B (a) Write the electron arrangement for atom A... 54

55 (b) A and B can form a compound (i) What type of bond holds atom A and B together? (ii).. What will happen to atom A during the formation of the compound with atom B?.. (iii) Draw the electron arrangement of the compound formed in (b)(ii). (iv) State one physical property of the compound formed... (c) Carbon atom, C, with an electron arrangement of 2.4 can combine with atom B to form a compound. (i) What is the molecular formula of the compound formed?. (ii) If the relative atomic masses of carbon is 12 and B is 32, what is the relative molecular mass of the compound in c(i)... Activity 9 1 The diagram below shows the proton number and the nucleon number for three atoms of elements, E, G and W. The letters used do not represent the actual symbols of the elements E 23 G W 55

56 (a) Construct a table to show the information of the three elements in terms of The number of protons The number of neutrons The electron arrangement The number of valence electrons [4 marks] Answer: (b) The reaction between atoms of element G and W forms an ionic compound whereas the reaction between atoms of element E and W forms a covalent compound. Explain how these ionic and covalent compounds are formed. Answer: (Ionic compound) Answer: (Covalent compound) 56

57 ( c) The ionic compound formed from the reaction between atoms of element G and W does conduct electricity when it is in solid state but can conduct electricity when dissolved in water. Answer: Describe an experiment to investigate this property. [8 marks] 57

58 CHAPTER 6: ELECTROCHEMISTRY A ELECTROLYTES AND NON-ELECTROLYTES Learning Outcomes: You should be able to: state the meaning of electrolyte, classify substances into electrolytes and non-electrolytes. relate the presence of freely moving ions to electrical conductivity. Activity 1 1. State the meaning of electrolyte: An electrolyte is a substance that can conduct (a) in (b) state or (c). (d). and undergo (e) (f) A non-electrolyte is a substance that cannot conduct (g). either in (h). state or (i).. solution. 3. Ionic compounds in molten state or in aqueous solution are electrolytes because these substances contain freely (j).. 4. Covalent compounds are non-electrolytes and these substances contain neutral (k)... and no freely (l) However, certain covalent compounds such as hydrogen chloride, ammonia and ethanoic acid when dissolved in water are electrolytes. This is because these compounds react with water to produce freely (m).. 58

59 5. Ionic compounds in molten state or in aqueous solution are electrolytes while covalent compounds and ionic compounds in solid state are non-electrolytes. Metals are nonelectrolytes but are good conductors of electricity. Classify the substances in the text box below into electrolyte and non-electrolyte Solid lead(ii) chloride, molten aluminium oxide, lead(ii) nitrate solution, solid sodium chloride, sodium chloride solution, magnesium, molten lead(ii) chloride, glucose solution, glacial ethanoic acid, dilute ethanoic acid, molten naphthalene, ethanol, silver, tetrachloromethane, sodium hydroxide solution, aqueous ammonia Electrolyte Non-electrolyte 59

60 B ELECTROLYSIS OF MOLTEN COMPOUNDS Learning Outcomes: Activity You should 2 be able to: 1. What describe do electrolysis, you understand by the term electrolysis? Electrolysis describe electrolytic is a process cell, whereby compounds in (a)... or (b).. identify cations and anions in a molten compound, states describe are evidence broken for down the (or existence decomposed) of ions held into their in a lattice constituent in solid (c) state but move freely by in passing molten state, (d). through them. describe electrolysis of a molten compound, 2. Anode write half-equations is the electrode for the discharge which of connected ions at anode to the and cathode, (e). terminal of a battery. predict products of the electrolysis of molten compounds. 3. Cathode is the electrode which is connected to the (f) terminal of a battery. 4. Carbon or platinum is chosen as electrodes as they are chemically inert or unreactive. 5. The diagram below shows the set-up of apparatus of electrolysis of molten lead(ii) bromide. Name the main apparatus and materials in the diagram. Activity 3 1. Diagram 3.1 shows the relationship between the presence of freely moving ions and electrical conductivity. The box below shows a list of statements that explain the why ionic compound in solid state do not conduct electricity but will conduct electricity in aqueous solution. The statements are arranged in random order. Choose the correct statement from the box below and write it into the correct text box in Diagram 3.1. During electrolysis cations are attracted to the cathode and anions are attracted to the anode. Solid sodium chloride contains sodium ions and chloride ions which are in fixed position and not freely moving. In solid state, sodium ions and chloride ions are strongly attracted by electrostatic forces in a lattice. Electric circuit is complete due to the flow of electrons along the connecting wires and movement of ions in the solution. If the electrodes are placed further apart, the ammeter reading will decrease because there will be an increase in internal resistance. Aqueous sodium chloride contains freely moving ions to conduct electricity. 60

61 Diagram

62 2. Colour all the cations red and the anions blue in solid sodium chloride and in the electrolyte in Diagram 3.1 above. Activity 4 1. Given below is a list of ionic compounds in molten state. Identify the cation and anion in each electrolyte. Electrolyte (Molten) Sodium chloride Cation Anion Name Formula Name Formula Lead(II) oxide Potassium bromide 2. Given below is a list of electrolytes and products discharged at both electrodes. Based on the given substance discharged at the electrode, write a half equation to represent the reaction occurring at the electrode. Electrolyte (molten) Substance discharged at the electrodes and the half equation Anode Cathode (i) Aluminium oxide Oxygen gas Half equation:.. Aluminium Half equation:.. (ii) Potassium iodide Iodine Half equation: Potassium Half equation:.. (iii) Sodium chloride Chlorine gas Half equation:.. Sodium Half equation:. (iv) Zinc bromide Bromine gas Half equation:.. Zinc Half equation:. 62

63 Activity 5 1 The flow chart below is used to predict the products formed at the electrodes during the electrolysis of molten lead(ii) bromide. Molten lead(ii) bromide Consists of (Ions that are present) a b ( Movement of ions) To anode To cathode c d (Half equation) At Anode At Cathode e f (Products formed) At Anode At Cathode g 2. In the spaces below, draw a similar flow chart (as in question 1) to predict the products formed at the electrodes from the electrolysis of molten zinc chloride, ZnCl 2. 63

64 C ELECTROLYSIS OF AQUEOUS SOLUTION Learning Outcomes: You should be able to: identify cations and anions in an aqueous solution, describe the electrolysis of an aqueous solution, explain using examples factors affecting electrolysis of an aqueous solution, write half equations for the discharge of ions at the anode and the cathode, predict the products of electrolysis of aqueous solutions. Activity 6 1. State three factors that may influence the selective discharge of ions during the electrolysis of an aqueous solution. (a) (b). (c). 2. In an aqueous solution of sodium chloride, apart from sodium ions, Na + and chloride ions, Cl --, ions, and.ions, from the slight dissociation of water are also present. 3. List the electrochemistry series (cations and anions) in order of increasing ease of discharge. Ease of discharge increases Cation:. Anion:.. 4. The following statements refer to the factors that affect the electrolysis of an aqueous solution. Fill in the blanks. (a) (b) The ions that are placed in the electrochemical series will be.. discharged. If the concentration of a particular ion is, the ion is.. (c) In the electrolysis of copper(ii) sulphate, CuSO 4..using copper electrodes, no ions are discharged at the anode. Instead, the copper anode and in the electrolyte. 64

65 Activity 7 The diagram below shows the set-up of apparatus of an electrolytic cell containing concentrated copper(ii) sulphate solution. Two test tubes filled with copper(ii) sulphate solution were placed over the electrodes J and K to collect any gas evolved. The switch is then turned on so that electrolysis of copper(ii) sulphate solution can occur. (a) Identify the cations and the anions present in the aqueous solution. Cations:.. Anions:.. (b) Identify which electrode ( J or K ) is the anode and the cathode: Anode.. Cathode. (c) (i) Which ion is selectively discharge at the anode? (ii) Give a reason for your answer in (c) (i) (iii) What do you observe at the anode? (iv) Give one test to confirm the gas released at K.. (v) Write a half equation to represent the discharge of ions at anode.. (d) (i) Which ion is selectively discharge at the cathode? (ii) Give a reason for your answer in (d) (i). (iii) Which do you observe at the cathode? (iv) Write a half equation to represent the discharge of ions at the cathode... (e) What do you observe about the copper(ii) sulphate solution?.. 65

66 Activity 8 (a) The table below shows two electrolytic cells with electrolytes of different concentration. You are required to answer each section by writing your answer in the spaces provided. 1. In the diagrams, label the cathode with the symbol and the anode with the symbol Show the direction of the flow of the electrons with arrowheads, > 3. Write the formula of all ions in the electrolyte. 4. a. Write the formula of ions which are attracted to the cathode. b. Underline the formula of ion which is selectively discharged. c. State the factor that affect the selective discharged of ion 5. Write the half equation to represent the reaction at the cathode. 6. What will you observe at the cathode? 7. a. Write the formula of ions which are attracted to the anode. b. Underline the formula of ion which is selectively discharged. c. State the factor that affect the selective discharged of ion 8. Write the half equation to represent the reaction at the anode. 9. What will you observe at the anode? 66

67 (b) The table below shows two electrolytic cells with the same electrolytes with different electrodes. You are required to answer each section by writing your answer in the spaces provided. 1. In the diagrams, label the cathode with the symbol and the anode with the symbol Show the direction of the flow of the electrons with arrowheads, > 3. Write the formula of all ions in the electrolyte. 4. a. Write the formula of ions which are attracted to the cathode. b. Underline the formula of ion which is selectively discharged. c. State the factor that affect the selective discharged of ion 5. Write the half equation to represent the reaction at the cathode. 6. What will you observe at the cathode? 7. a. Write the formula of ions which are attracted to the anode. b. Underline the formula of ion which is selectively discharged. c. State the factor that affect the selective discharged of ion 8. Write the half equation to represent the reaction at the anode. 9. What will you observe at the anode? 10 What do you observe about the copper(ii) sulphate solution? 67

68 Explain D ELECTROLYSIS IN INDUSTRIES Learning Outcomes: You should be able to: state uses of electrolysis in industries, explain the extraction, purification and electroplating of metals involving electrolysis in industries, write chemical equations to represent the electrolysis process in industries, justify uses of electrolysis in industries, describe the problem of pollution from electrolysis in industry. Activity 9 1. Fill in the blanks. The application of electrolysis in industries are (a). (b) and (c) In the extraction of aluminium from its ore, (d). electrodes are used and (e)... is added to aluminium oxide to lower its melting point. In purification of metals, the pure metal is made the (f).. and the impure metal is made the (g).. The electrolyte used is an aqueous salt solution of the metal ions. In electroplating of metals, the (h)...is made the anode and the (i) to be (j) is made the cathode. The electrolyte used is an aqueous salt solution of the electroplating metal. The purposes of electroplating metals are to make the electroplated object more (k).. and (l).. to corrosion. 2. Below are shown the three uses of electrolysis in industries. Fill in the blanks. 1. Substance used as cathode and anode Extraction of aluminium from bauxites Cathode: Anode: Purification of copper from impure mined copper Cathode: Anode: Electroplating of iron spoon with silver Cathode: Anode 2. Electrolyte used 68

69 3. Half equation representing the process. Cathode: Anode: Cathode: Anode: Cathode: Anode: E VOLTAIC CELLS Learning outcomes: You should be able to: describe the structure of a simple voltaic cell and Daniell cell, explain the production of electricity from a simple voltaic cell, explain the reactions in a simple voltaic cell and Daniell cell, compare and contrast the advantages and disadvantages of various voltaic cells, describe the differences between electrolytic and voltaic cells. Activity A simple voltaic cell can be constructed by immersing two. metals in an. connected by 2. In a voltaic cell, energy is converted to. energy. 3. THE ELECTROCHEMICAL SERIES is an arrangement of metals based on the tendency of each metal atom to donate electrons. Complete the table below. K Electrochemical series of metals Cation formed and number of electron(s) released during the process K + + e Al Tendency of metal atoms to donate electrons to form ions increases Al e * Note: Hydrogen is not a metal, but it is included in the Electrochemical Series 69

70 4. The diagram below shows an example of a simple voltaic cell. In the text box below are sentences explaining the production of electricity from a simple voltaic cell. The sentences are listed in random order. You are required to arrange these sentences in the best possible order so as to give a clear description of the reactions occurring in a simple voltaic cell. An example of a simple voltaic cell is a magnesium strip and a copper strip immersed in dilute sodium chloride solution. The electrons then flows from the magnesium ribbon to the copper plate through the wire and this results in the flow of electrical current. Hence magnesium atom releases electrons more easily than a copper atom and the magnesium act as the negative terminal of the cell. The overall equation for the reaction is given as follows. Mg(s) + 2H + (aq) Mg 2+ (aq) + H 2 (g) Magnesium is placed higher than copper in the electrochemical series. At the negative terminal, each magnesium atom releases two electrons and the Mg 2+ formed moved into the solution. Mg(s) Mg 2+ (aq) + 2e At the positive terminal which is the copper plate, the electrons are accepted by the H + ions in sodium chloride solution. 2H + + 2e H 2 (g) [If you have any problem, you can refer to page 104 of the text book for guidance.] Answer: (a) (b) (c).. 70

71 (d) (e) (f) (g)... Activity (a) Draw and label the set-up of apparatus of a Daniell cell consisting of a salt bridge. (b) (i) Which metal in the Daniell cell is the negative terminal? (ii) Give reason for your answer in (b)(i). (iii) Write a half equation to represent the reaction occurring at the negative terminal.. (c) Write a half equation to represent reaction at positive terminal. (d) What do you observe at (i) negative terminal.. (ii) positive terminal.. (e) State two functions of the salt bridge

72 2. The table below listed are five types of voltaic cells commonly used in our daily lives. Each voltaic cell has its advantages and disadvantages. Complete the table by stating the advantages and disadvantages of each voltaic cell. Voltaic cell 1. Leadacid accumulato r Advantage s Disadvantage s 2. Dry cell 3. Mercury cell 4. Alkaline cell 5. Nickelcadmium cell Activity 12 What are the differences between an electrolytic cell and a voltaic cell? Table 12.1 are statements showing differences between an electrolytic cell and a voltaic cell. Complete Table 12.2 by choosing the correct matching statements. It does not require a source of electric current The electrical energy causes chemical reactions to occur at the electrodes. Electrical energy chemical energy The electrodes must be of two different metals Electrons flow from the positive electrode (anode) to the negative electrode (cathode). Ions receive electrons at the positive terminal. (Reduction) Ions receive electrons at the negative terminal. (Reduction) It requires a source of electric current The chemical reaction that occur at the electrodes produces electric current. Chemical energy electrical energy The electrodes may be of the same material such as carbon Electrons flow from the more electropositive metal (negative terminal) to the less electropositive metal (positive terminal). Ions donate electrons at the positive terminal. (Oxidation) Ions donate electrons at the negative terminal. (Oxidation) Table

73 DIFFERENCES Electrolytic cell Aspect Chemical cell Source of electric current Conversion of energy Type of electrodes Direction of flow of electrons Type of reaction at positive terminal Type of reaction at negative terminal 73

74 Chemistry Form 4 F THE ELECTROCHEMICAL SERIES Learning Outcomes: You should be able to: describe the principles used in constructing the electrochemical series, construct the electrochemical series, explain the importance of electrochemical series, predict the ability of a metal to displace another metal from its salt solution, write the chemical equations for metal displacement reactions. Activity 13 Three experiments were conducted to investigate the potential differences between three pairs of metals in a voltaic cell. An electrochemical series for four metals P, Q, S and T is then constructed based on the potential difference obtained. Three pair of metals used as electrodes in different voltaic cells are: P and Q, Q and S and S and T. All the metals are cleaned with sandpaper before used. 50 cm 3 of 1.0 mol dm -3 sodium nitrate solution is poured into a beaker as electrolyte. Experiment I The electrodes P and Q are immersed into the solution. The two electrodes are connected to a voltmeter using copper wires. Electrode Q is the positive terminal. The voltmeter reading is recorded. Experiment II The electrodes Q and S are immersed into the solution. The two electrodes are connected to a voltmeter using copper wire. Electrode Q is the positive terminal. The voltmeter reading is recorded. Experiment III The electrodes S and T are immersed into the solution. The two electrodes are connected to a voltmeter using copper wire. Electrode T is the positive terminal. The voltmeter reading is recorded. Based on Experiment I, II and III, answer the questions below. (a) Record the voltmeter reading of each experiment in the spaces provided. Experiment 1 Experiment II Experiment III V V V 5 6 Voltmeter reading:. Voltmeter reading: Voltmeter reading:... (b) Construct a table to record the data from the above experiments. 74

75 Chemistry Form 4 (c) List the apparatus and materials that you will need to carry out this experiment. Apparatus:... Materials:.. (d) State all the variables: 1. Manipulated variable:.. 2. Responding variable:. 3. Controlled variable: (e) State the hypothesis:... (f) Based on the information obtained in Experiment I, what can you infer about metal P and Q? (g) Write a half equation for the reaction occurring in negative of Experiment I, assuming the cation has a +2 charge.. (h) Arrange the metals P, Q, S and T in descending order of their tendency to donate electrons.... (i) Another voltaic cell is set-up using metals T and Q as electrodes. Predict the potential difference produced in the cell... (j) Given that metal X is placed between metal S and metal Q in the electrochemical series, can metal X displace metal S from its salt solution? Give an explanation for your answer.. (k) Given that copper is more electropositive than metal T, a displacement reaction will occur when copper is immersed into a salt solution of metal T, TNO 3. Write the chemical equation for this reaction.. (l) State three important uses of the electrochemical series Activity 14 : Displacement Reactions 1. Metals placed up in the Electrochemical series ar able to displace metals placed. them from their salt solutions. 75

76 Chemistry Form 4 K > Na > Ca > Mg > Al > Zn > Fe Sn > Pb > H > Cu > Ag 2. Example : Ewacrion between xinc and copper(ii) sulphate solution Chemical equation : Zn + CuSO is place higher position than in electrochemical series,,.. is more electropositive than.., hence.. can displace from. solutions. Copper(II) sulphate solution zinc Observation: 1. Zinc. 2.. Solid formed 3. Intensity of blue solution. Zinc atom releases 2 electrons to form zinc ion, Zn 2+ : Half equation :. Copper(II) ion Cu 2+ receives 2 electrons to form copper atom : Half equation :.. Ionic equation :. 3. Experiment : To construct the electrochemical series using the principle of displacement of metals (Displacement Reaction) Problem Statement : Hypothesis: The greater the number of metals that can be displaced by a metal from their solutions, the higher is its position in the electrochemical series. Variables: Manipulated variable : Responding variable : Fixed variables : List of Materials and Apparatus: Test tubes, sand paper, 1 mol dm -3 zinc nitrate solution, 1 mol dm -3 lead (II) nitrate solution, 1 mol dm -3 copper (II) nitrate solution, magnesium strips, zinc strips, lead strips and copper strips. magnesium zinc Lead(II) copper(ii) nitrate nitrate nitrate nitrate solution solution solution solution magnesium strips 76

77 Chemistry Form 4 Procedure: 1. Pour 5 cm 3 of magnesium nitrate solution, zinc nitrate solution, lead (II) nitrate solution, and copper (II) nitrate solution into four separate test tubes. 2. For each test tube, place a strip of magnesium into each solution. 3. Record all the observations. 4. Repeat steps 1 to 3 using strips of zinc, lead and copper to replace the magnesium strip. For each repetition, use a fresh salt solution. Data and Observation Complete this table please! Metal strip Salt solution Magnesium nitrate solution Zinc nitrate solution Lead (II) nitrate solution Copper (II) nitrate solution Magnesium Zinc Lead Copper a. Which metal can displace the most number of other metals from their solutions?. b. Write the half equation of the reaction occurred in magnesium strip for this experiment. c. Which metal can be displaced by all other metals in the experiment?.. d. Arrange the metals in descending order based on the electrochemical series and the number of metals displaced by it. e. Write the ionic equations to show all displacement reactions by zinc

78 Chemistry Form 4 CHAPTER 7: ACIDS AND BASES A ACIDS AND BASES Learning Outcomes You should be able to: State the meaning of acid, base and alkali State uses of acids, bases and alkalis in daily life Explain the role of water of water in the formation of hydrogen ions to show the properties of acids Explain the role of water in the formation of hydroxide ions to show the properties of alkalis Describe chemical properties of acids and alkalis Activity 1 Meaning of acid,base and alkali Fill in the blanks with the correct words: 1 An acid is a chemical substance which ionises in. to produce.ions. The hydrogen ion combines with a water molecule, H 2 O to form a.. ion, H 3 O +. 2 Acid can be classified as a.acid or a.acid based on its basicity. 3 Basicity is the number of ionisable. atoms per molecule of an acid. 4 A base is a substance that reacts with an acid to form a... and. only. Bases include metal hydroxides and metal oxides. 5 Give the names of acids, their formulae and its basicity: (i) Hydrochloric acid Name of acid Formula of acid Basicity (ii) H 2 SO 4 (iii) HNO 3 (iv) Ethanoic acid 6 Complete the ionization of acids below : a) b) c) d) HCl (aq).... (aq) + Cl - (aq) (aq) H + (aq) + - NO 3 (aq) H 2 SO 4 (aq). +.. CH 3 COOH (aq). + CH 3 COO - (aq) (Refer to page F4 Chemistry textbook) 78

79 Chemistry Form 4 Activity 2 : Fill in the blanks with correct words: 1 A base is a substance that reacts with an acid to form...only. An alkali is a water-soluble base which ionises in water to produce.....,oh - 2 Complete the table below Name of alkali (i) Sodium hydroxide (ii) (iii) Ammonia aqueous Formula of alkali KOH 3 Complete the ionization of following alkalis : NaOH (aq). (aq) + OH - (aq) + (aq) + H 2 O (l) NH 4 (aq) +. (aq) 4 Uses of acids, bases and alkalis (a) To use as. reagent Example: sodium hydroxide solution, sulphuric acid, hydrochloric acid (b) To... Example: Ethanoic acid (vinegar), benzoic acid (c)to make various.. Example: Magnesium oxide antacid medicine, Ascorbic acid vitamin C (d)to produce., detergent and Example: sodium hydroxide to make soap and detergent Magnesium hydroxide added to tooth-paste (e)to manufacture dyes,. and drugs Example: methylamine (f)used in rocket fuel Example: (Refer to page F4 Chemistry textbook) Activity 3: Role of water and its properties of acids and alkalis Fill in the blanks with correct words. 1 An acid only shows its.. properties when dissolve in. 2 In the presence of water, the acid ionises to form..ions. 79

80 Chemistry Form 4 3 Without water, an acid still exists as and there are no... ions present. Glacial Ethanoic acid, CH 3 COOH is an example of acidic substance. Complete the following table to show the role of water in acidic properties. Condition of ethanoic acid Glacial ethanoic acid, Ethanoic acid in water Ethanoic acid in dry propanone ( organic solvent ) Effect on the blue litmus paper Inference 5 An alkali only shows its.. properties when dissolve in.. 6 In the presence of water, the base dissociates to produce... ions that are responsible for the properties 7 Ammonia,NH 3 is an example of alkali. Complete the table below to show the role of water in alkaline properties. Condition of ammonia Effect on the red litmus paper Inference Dry Aqueous (dissolved in water) Dissolved in propanone, (organic solvent) (Refer to page F4 Chemistry textbook and page F4 Chemistry Practical Book ) Activity 4: Properties of acids and alkalis Tick ( ) Statement True or False 1. All acids are dangerous 2. All alkalis are dangerous 3. Acids taste sweet 4. Alkalis taste bitter 5. Acids taste sour 6. Most acids can burn skin 7. Alkalis feel soapy 8. Acids produce H + ions in solution 9. Acids produce OH - ions in solution 10. Acids can corrode 11. Acids have a ph above 7 80

81 Chemistry Form Acids have a ph below Alkalis turn moist red litmus paper blue 14. Acids turn moist red litmus paper blue (Refer to page F4 Chemistry textbook and page F4 Chemistry Practical Book ) Activity 5 : Chemical properties of acids 1 Acids react with bases to form salts and water only. Bases are metal oxides or metal hydroxide. Write the chemical equation for the reaction between sulphuric acid and copper(ii) oxide Acids react with reactive metals to produce salts and hydrogen gas. Write the chemical equation for the reaction between hydrochloric acid and zinc Acids react with metal carbonates to produce salts, water and carbon dioxide gas. 81

82 Chemistry Form 4 Write the chemical equation for the reaction between nitric acid and calcium carbonate.... Activity 6 : Chemical properties of alkalis 1 Alkalis react with acids to form salts and water only Write the chemical equation for the reaction between sodium hydroxide and benzoic acid When a mixture of an alkali and an ammonium salt is heated, ammonia gas is liberated. Write the chemical equation for the reaction between sodium hydroxide and ammonium chloride Alkalis react with most metal ion solutions ( cations ) to produce the insoluble metal hydroxides or precipitate - (precipitation reaction) 82

83 Chemistry Form 4 Write the chemical equation for the reaction between sodium hydroxide and iron(ii) sulphate.... (Refer to page F4 Chemistry textbook and page 91- F4 Chemistry Practical Book ) B: The strength of acids and alkalis Learning Outcomes: You should be able to: State the use of a ph scale Relate ph value with acidic or alkaline properties of a substance Relate concentration of hydrogen ions with ph value Relate concentration of hydroxide ions with ph value Relate strong or weak acid with degree of dissociation Conceptualise qualitatively strong and weak acids Conceptualise qualitatively strong and weak alkalis Activity 7: The ph scale Fill in the blanks with correct words 1 The ph scale ( 0 to 14 ), is used to indicate the degree of or. of a solution. 2 ph value less than 7, indicates an solution ph value equal to 7, indicates a solution ph value more than 7, indicates an solution 3 ph value can be determined by using...,ph paper or indicator. 4 Acids Neutral Alkalis Acidity...(increase or decrease ) (Refer to page 121 Chemistry text book) Alkalinity...(increase or decrease ) 83

84 Chemistry Form 4 Activity 8 : Strong and weak acid 1. Complete the flowchart below to understand the concept of strong acid and weak acid Strong acid Weak acid Degree of dissociation Ionization in water Concentration of ions ph value Activity 9: Strong and weak alkali Examples 1. Complete the flowchart below to understand the concept of strong alkali and weak alkali. Strong alkali Weak alkali Degree of dissociation Ionization in water Concentration of ions ph value Examples 84

85 Chemistry Form 4 C: CONCENTRATIONS OF ACIDS AND ALKALIS Learning Outcomes You should be able to: State the meaning of concentration State the meaning of molarity State the relationship between the number of moles with molarity and volume of a solution Describe the methods for preparing standard solutions Describe the preparation of a solution with a specified concentration using dilution method Relate ph values with the molarity of acids and alkalis Solve numerical involving molarity of acids and alkalis Activity 10 : Concentration of acids and alkalis Fill in the blanks with the correct answers. 1 2 The concentration of a solution refers to the quantity of solute in 1dm 3 of solution Concentration can be defined in two ways :- (a) Concentration in g dm -3 = (b) Concentration in mol dm -3 = (Concentration in mol dm -3 is also known as molarity or molar concentration (M ) ) 2 The two units of concentration can be inter-converted: Concentration in... X Molar mass Concentration in... Molar mass Work this out g of copper(ii) sulphate is dissolved in water to form 500 cm 3 solution. Calculate the concentration of copper(ii) sulphate solution in g dm -3? [Answer: 10.0 g dm -3 ] 4 What is the mass of sodium carbonate required to dissolve in water to prepare 200 cm 3 solution that contains 50 g dm -3? [Answer: 10 g] (Refer to page F4 Chemistry textbook ) 85

86 Chemistry Form g of sodium carbonate powder, Na 2 CO 3, is dissolved in water and made up to 250 cm 3. What is the molarity of the sodium carbonate solution? [Relative atomic mass: C, 12; O, 16; Na, 23] [Answer: 0.15 mol dm -3 ] Activity 11 The number of moles of solute, n in a given volume of solution V and the molarity of M can be calculated by using the formula : n = MV n = Number of moles of solute M = Molarity of solution (mol dm -3 ) V = Volume of solution (dm 3 ) If the volume is in cm 3 convert the volume of solution from cm 3 to dm 3 n = MV 1000 or n = M x V Calculate the number of moles of ammonia in 150 cm 3 of 2 mol dm -3 aqueous ammonia. [Answer: 0.3 mol] 6 A student pipetted 20.0 cm 3 of potassium hydroxide, KOH solution into a conical flask. The concentration of the alkali was 1.5 mol dm -3. Calculate the number of moles of potassium, KOH in the flask. [Answer: 0.03 mol dm -3 ] 7 Calculate the number of moles of hydrogen ions present in 200 cm 3 of 0.5 mol dm -3 sulphuric acid, H 2 SO 4. [Answer: 0.2 mol of H + ions] Activity 12 : Preparation of Standard solutions 1 What is a standard solution? 86

87 Chemistry Form 4 2 Preparation of standard solutions by Weighing method (mass of solute) :- Step 1 : Calculate the mass of solute needed. mass = n X molar mass = MV X molar mass 1000 Example: To prepare 100 cm 3 of 2.0 mol dm -3 sodium hydroxide solution. Calculate the mass of NaOH needed. [Relative atomic mass: Na, 23 ; O, 16 ; H, 1] mass = n X molar mass n = mass molar mass n = MV 1000 = MV X molar mass 1000 = 2.0 X 100 X 40 = 8 g 1000 Try this: (a) To prepare 250 cm 3 of 1.0 mol dm -3 sodium carbonate solution. Calculate the mass of Na 2 CO 3 needed. [Relative atomic mass: Na, 23 ; O, 16 ; C, 12] [Answer : 26.50g] (b) 0.25 mol dm -3 solution of sodium hydroxide was prepared by dissolving x g of sodium hydroxide in 750 cm 3 of water. What is the value of x? [Relative atomic mass: Na, 23 ; O, 16 ; H, 1] (Refer to page F4 Chemistry textbook ) Step 2 : Match the descriptions / procedures with the correct diagram below. [Answer : 7.5 g] Wash and rinse the weighing bottle or small beaker and filter funnel to ensure no solute remains in any of the apparatus used. Transfer the dissolved solute into a suitable volumetric flask. (a) 87

88 Chemistry Form 4 Add water slowly by using a dropper to bring the level of the solution to the calibration mark. The volumetric flask is closed tightly and inverted several times to get a uniform or homogenous solution. (b) Calculate the mass of solute needed. Weigh out the exact mass of solute needed in a weighing bottle. Dissolved the solute in a small amount of distilled water. (c) Add more water carefully to the volumetric flask and swirl gently. Shake well to ensure thorough mixing. (d) Activity 13 : Preparation of Standard solutions by Dilution method 1 Dilution method Step 1 : Calculate the volume of stock solution required by using the equation:- M 1 V 1 = M 2 V 2 M 1 = molarity of solution before dilution V 1 = volume of solution before dilution M 2 = molarity of solution after dilution V 2 = volume of solution after dilution When using the equation M 1V 1 = M 2V 2, make sure that both V 1 and V 2 are of the same unit. Example: 50 cm 3 of 0.1 mol dm -3 sodium hydroxide, NaOH solution from 2.0 mol dm -3 sodium hydroxide,naoh solution Before dilution After dilution M 1 V 1 M 2 V mol dm -3? 0.1 mol dm cm x V 1 = 0.1 x 50 V 1 = 0.1 x 50 = 2.5 cm Try this: 100 cm 3 of 0.5 mol dm -3 potassium manganate(vii),kmno 4 solution is prepared from 1.0 mol dm -3 potassium manganate(vii),kmno 4 solution. Calculate the volume of the solution 88

89 Chemistry Form 4 (a) (b) [Answer : 50 cm 3 ] Step 2 Match the diagram with the correct descriptions below. Add water slowly by using a dropper to bring the level of the solution to the calibration mark. The volumetric flask is closed tightly and inverted several times to get a uniform or homogenous solution. Transfer the stock solution to a suitable volumetric flask. (c) Calculate the volume of stock solution required. (d) Use a pipette to draw up the required volume of stock solution. Activity 14 : The ph values and molarity of acids and alkalis Fill in the blanks with correct words. Use words given in the box. Increases decreases concentration hydrogen dissociation higher hydroxide alkali 1 The ph value of an acid or an alkali depends on three factors : (a) degree of. (b) molarity or.. (c).. of the acid or.. 2 The lower the ph value, the.. the concentration of ions. 3 The higher the ph value, the.. the concentration of... ions. 4 As the molarity of an acid increases, the ph value of the acid. The ph value of an alkali increases when the molarity of the alkali... (Refer to page F4 Chemistry textbook ) 89

90 Chemistry Form 4 D : NEUTRALISATION Learning Outcomes You should be able:- Explain the meaning of neutralisation. Write equations for neutralisation Explain the applications of neutralization in daily life Describe the titration process of acid-base Determine the end-point of titration during neutralization Solve numerical problems involving neutralisation Activity 15 : Neutralisation 1 What is the meaning of neutralisation?.. 2 What are the only products of neutralisation?. 3 Write a balanced chemical equation for the neutralisation of the following reactions:- (a) nitric acid and barium hydroxide (b) sulphuric acid and sodium hydroxide (c) phosphoric acid and calcium hydroxide (d) ethanoic acid and potassium hydroxide 4 Complete the flow chart below:- 90

91 Chemistry Form 4 (Refer to page F4 Chemistry textbook ) Activity 16 : Acid base Titration 1 What is a titration?. 2 What is the function of an indicator?.. 3 Complete the table below. Indicator Red litmus paper Blue litmus paper Phenolphthalein Methyl orange Colour in solution Acid Neutral Alkali 4 Write out the procedure for carrying out an acid-base titration to determine the volume of nitric acid 0.5 mol dm -3 needed to neutralise 25 cm 3 potassium hydroxide 0.5 mol dm -3. Label the diagram. 91

92 Chemistry Form 4 (Refer to page 130 F4 Chemistry textbook and Page 103 F4 - Chemistry Practical Book) Activity 17 : Numerical problems involving neutralisation Useful equations in solving numerical problems involving neutralisation.: n = mass molar mass n = MV MaVa = a MbVb b n = no of moles M = Molarity of solution V = Volume of solution in dm 3 Ma = molarity of acid Mb = molarity of alkali Va = volume of acid Vb = volume of alkali a and b = mole ratio of acid to alkali in a balanced chemical equation Example: In an experiment, 25 cm 3 of sodium hydroxide solution, NaOH of unknown concentration required cm 3 of 1.0 mol dm -3 sulphuric acid, H 2 SO 4 for complete reaction in titration. Calculate the molarity of sodium hydroxide. Write out a balanced chemical equation: MaVa 1 MbVb = 2, 1.0 X = 1 Mb X H 2 SO 4 + 2NaOH Na 2 SO 4 + 2H 2 O a = 1 mol b = 2 mol Mb = 2 X 1.0 X = 2.12 mol dm -3 (Molarity of sodium hydroxide) What is the volume of 1.5 mol dm -3 aqueous ammmonia required to completely neutralise cm 3 of 0.5 mol dm -3 sulphuric acid? 2NH 3 + H 2 SO 4 (NH 4 ) 2SO 4 92 [Answer: 20 cm 3 ]

93 Chemistry Form 4 2 Calculate the volume in cm mol dm -3 hydrochloric acid that is required to react completely with 2.65 g of sodium carbonate. [Relative atomic mass: Na, 23 ; O, 16 ; C, 12] 3 25 cm 3 of sulphuric acid was neutralised with 18.0 cm 3 of sodium hydroxide 1.0 mol dm -3. Calculate (a) the number of moles of sulphuric acid that is used in this reaction. (b) the molarity of sulphuric acid [Answer: 25 cm 3 ] [Answer (a) mol (b) 0.36 mol dm -3 ] 4 24 cm 3 of 0.1 mol dm -3 NaOH is required to completely neutralise 20.0 cm 3 of sulphuric acid. Calculate the concentration of sulphuric acid in (a) mol dm -3 (b) g dm [Answer (a) 0.06 mol dm -3 (b) 5.88 g dm -3 ]

94 Chemistry Form 4 5 What is the molarity of phosphoric acid if 15 cm 3 of the acid is neutralized by 38.5 cm 3 of 0.15 mol dm -3 NaOH? Activity 18 [Answer (a) mol dm -3 ] 1 A student carried out an experiment to determine the end-point for the titration of 25.0 cm 3 of 1.0 mol dm -3 sodium hydroxide solution with hydrochloric acid. Phenolphthalein is used as the acid-base indicator. Table 1 shows the three titrations that were conducted and the magnification of the burette readings. Titration No. I II III 1 hydrochloric acid hydrochloric acid 26 hydrochloric acid 2 27 Initial burette reading hydrochloric acid 26 hydrochloric acid 39 hydrochloric acid 27 Final burette reading. Table 1 94

95 Chemistry Form 4 (a) Record the burette readings for the three titrations in the space provided in Table 1. (b) Construct a table and record the initial burette reading, final burette reading and the volume of acid used for each titration. (c) Calculate the average volume of hydrochloric acid used in the experiment. (d) Calculate the concentration of hydrochloric acid used in the experiment. (e) If the experiment is repeated by replacing 1.0 mol dm -3 of hydrochloric acid with 1.0 mol dm -3 of sulphuric acid, predict the end-point of the titration.. (f) Acids can be classified into strong acid and weak acid. Classify the following acids into strong acids and weak acids. Ethanoic acid, hydrochloric acid, sulphuric acid, carbonic acid, nitric acid, Strong acids Weak acids 95

96 Chemistry Form 4 (g) State the colour change of the phenolphthalein indicator at the end point of titration. (h) If phenolphthalein is replaced with methyl orange as the acid-base indicator, state the colour change. (i) Write a chemical equation for the neutralisation reaction between hydrochloric acid and sodium hydroxide.. 96

97 Chemistry Form 4 CHAPTER 8 : SALTS A. SYNTHESISING SALTS Learning Outcomes You should be able to: state examples of salts used in daily life, explain the meaning of salt identify soluble and insoluble salts, describe the preparation of soluble salts, describe the purification of soluble salts by recrystallisation, list physical characteristics of crystals, describe the preparation of insoluble salts, write chemical and ionic equations for reactions used in the preparation of salts, design an activity to prepare a specified salt, construct ionic equations through the continuous variation method solve problems involving calculation of quantities of reactants or products in stoichiometric reactions Activity 1 : Meaning and uses of Salts 1. A salt is an.. formed when the.. ion, from an is replaced by a. ion or an..ion. 2. Example of salts : Complete the table below Acid Formula of acid Salt Formula Cation Anion Sodium chloride NaCl Na + Cl - Potassium carbonate K 2 CO 3 Copper(II) sulphate CuSO 4 Ammonium nitrate NH 4 NO 3 Magnesium nitrate Mg(NO 3 ) 2 Sodium ethanoate CH 3 COONa 3. Match the following salts with their uses. Salts Uses Barium sulphate BaSO 4 Fungicide Calsium sulphate CaSO 4 Bleaching agent Iron sulphate FeSO 4 Paint for yellow line on road Ammonium nitrate NH 4 NO 3 X-ray meals in hospital Copper(II) sulphate CuSO 4 Nitrogenous fertilizer Sodium chloride NaCl Toothpaste Sodium hydrogen carbonate Iron tablets, for anaemia patient Sodium nitrite NaNO 2 Baking powder Sodium hypochlorite Preserve food NaOCl Tin(II) fluoride SnF 2 A flavouring Lead(II) chromate PbCrO 4 Plaster of Paris for broken bone 97

98 Chemistry Form 4 Activity 2 : Identify soluble and insoluble salt. Ba 2+ Ca 2+ Pb 2+ Pb 2+ Ag + Hg SO 4 NO 3 Water Na + K + Cl - CO NH 4 Fill in the blanks with the correct word(s) 1. All.,., and. salts are soluble in water. 2. All. salts are soluble in water. 3. All sulphate salts are soluble in water except.. sulphate,. sulphate and sulphate. 4. All chloride salts are soluble in water except.. chloride,. chloride and chloride. 5. All carbonate salts are insoluble in water except.. carbonate,. carbonate and carbonate 6. State whether each of the following salt is soluble or insoluble in water No Formula of Salt Solubility (, X ) No Formula of Salt Solubility (, X ) 1 PbCO 3 21 MgCO 3 2 NaCl 22 KCl 3 CaSO 4 23 (NH 4 ) 2 SO 4 4 AgNO 3 24 Cu(NO 3 ) 2 5 K 2 CO 3 25 SnCO 3 6 FeCl 3 26 CaCl 2 7 Na 2 SO 4 27 BaSO 4 8 NH 4 NO 3 28 KNO 3 9 CuSO 4 29 Ag 2 CO 3 10 PbCl 2 30 MgCl 2 11 ZnCO 3 31 ZnSO 4 12 Ca(NO 3 ) 2 32 Ba(NO 3 ) 2 13 Na 2 CO 3 33 FeCO 3 14 AgCl 34 NH 4 Cl 15 PbSO 4 35 Fe(NO 3 ) 3 16 Pb(NO 3 ) 2 36 MgSO 4 17 (NH 4 ) 2 CO 3 37 BaCO 3 18 HgCl 2 38 ZnCl 2 19 Na 2 SO 4 39 FeSO 4 20 NaNO 3 40 Mg(NO 3 ) 2 98

99 Chemistry Form 4 Activity 3 : Write chemical and ionic equations for reactions used in the preparation of soluble salts 1. Complete these general equation for preparing soluble salts. a. metal + acid +. b. metal oxide (or metal hydroxide) + acid + c. alkali + acid +. d. metal carbonate + acid Using the general equations in question 1, complete the following chemical equation. It may also be necessary to balance the equation. a. Mg + H 2 SO 4 +. b. (i) CuO + HCl + (ii) Zn(OH) 2 + HNO c. NaOH + HCl.. +. d. MgCO 3 + H 2 SO Deduce the identity of the acid, metal, salt, or other product by filling in the missing details in this table of preparation of soluble salt Method of Preparation Reactants Salt Formed Other Product a) metal + acid Magnesium + Magnesium chloride Hydrogen b) metal oxide + acid Copper(II) oxide + sulphuric acid. c) metal carbonate + acid + Zinc sulphate Water +... d) metal hydroxide + acid + Potassium nitrate f) alkali + acid + Sodium chloride 99

100 Chemistry Form 4 4. Name the reactants which are needed to prepare the following soluble salts: (a) Copper(II) sulphate (b) Zinc chloride (c) Potassium nitrate :.. :. :.. (d) Ammonium sulphate :.. (e) Magnesium nitrate :.. 5. Rewrite each of the following chemical equation as ionic equation. Shown below is an example where a chemical equation can be simplified into an ionic equation. Example : Chemical equation : Zn(s) + H 2 SO 4 (aq) ZnSO 4 (aq) + H 2 (g) Zn + 2H SO 4 Zn SO 4 + H 2 (s) (aq) (aq) (aq) (aq) (g) Ionic equation : Zn(s) + 2H + (aq) Zn 2+ (aq) + H 2 (g) a. Chemical equation : Mg(s) + 2HCl(aq) MgCl 2 (aq) + H 2 O Ionic equation :... b. Chemical equation : MgO(s) + 2HCl(aq) MgCl 2 (aq) + H 2 O Ionic equation :... c. Chemical equation : NaOH (aq) + HNO 3 (aq) NaNO 3 (aq) + H 2 O (l) Ionic equation :... d. Chemical equation : CuCO 3 (s) + H 2 SO 4 (aq) CuSO 4 (aq) + CO 2 (g) + H 2 O (l) Ionic equation :

101 Chemistry Form 4 Activity 4 : Write out the procedure for the preparation of soluble salts of sodium, potassium and ammonium Soluble salt Name two chemical substances to prepare the salt Sodium Chloride, NaCl Chemical equation Procedure: (Diagram) Description Describe the physical characteristics of the crystals that you obtained 101

102 Chemistry Form 4 Activity 5 : Write out the procedure for the preparation of soluble salts (not sodium, potassium or ammonium salt) Soluble salt Copper(II) sulphate, CuSO 4 Name two chemical substances to prepare the salt 2. Chemical equation Procedure: (Diagram) Description Describe the purification process of the crystals 102

103 Chemistry Form 4 Activity 6 : Write chemical and ionic equations for reactions used in the preparation of insoluble salts 1. Insoluble salts can be prepared by.. method through.. reaction. In this reaction, two different aqueous solution mutually exchange their.. to form. Soluble salt solution + Soluble salt solution Insoluble salt MX containing cation M + containing anion X - Chemical equation : AgNO 3 (aq) + NaCl (aq) AgCl (s) + NaNO 3 (aq) Ionic equation : Ag + (aq) + Cl - (aq) AgCl (s) 2. Preparation of insoluble salts Example 1: Barium sulphate, BaSO 4 Solution 1:... Solution 2:.. Chemical equation :.... Ionic Equation :. Observation : White precipitate formed Example 2: Copper(II) carbonate, CuCO 3 Solution 1:.. Solution 2:. Chemical equation :. Ionic Equation :. Observation :.. precipitate formed Example 3: Lead(II) chromate(vi), PbCrO 4 Solution 1:.. Solution 2:. Chemical equation :. Ionic Equation :.. Observation :.. precipitate formed 103

104 Chemistry Form 4 Activity 7 : Describe the preparation of insoluble salts Insoluble salt Lead(II) iodide, PbI 2 Name two chemical substances to prepare the salt 2. Chemical equation Ionic equation Procedure: (Diagram) Description 104

105 Chemistry Form 4 Activity 8 : Construct ionic equation for the formation of lead(ii) chromate through the continuous variation method, Test tube 2 2.cm 3 of potassium chromate (VI), test tube 3 3 cm 3 varying the volumes of potassium chromate (VI) Fixed the volumes of lead (II) nitrate at 5.0 cm 3. Figure 1 Figure 1 shows seven test tubes for the reaction between lead(ii) nitrate Pb(NO 3 ) mol dm -3 and potassium chromate(vi) K 2 CrO mol dm -3. (a) Calculate the number of moles of lead(ii) nitrate Pb(NO 3 ) 2 and potassium chromate(vi) K 2 CrO 4 used in test tubes 1-7. Using a ruler, measure the height of lead(ii) chromate(vi) precipitate formed. Record all these in Table 1as well as complete Table 1. Test Tube Volume of Pb(NO 3 ) 2 /cm No of mole of Pb(NO 3 ) 2 Volume of K 2 CrO 4 /cm No of mole of K 2 CrO 4 Height of precipitate / cm Colour of solution above precipitate Table 1 105

106 Chemistry Form 4 (b) Based on Table 1, draw a graph of the height of the precipitate against volume of lead (II) nitrate solution on the graph paper. (c) On the graph that you have drawn in (b), (i) mark and write the minimum volume of potassium chromate(vi) solution needed for complete reaction with 5.0 cm 3 of lead(ii) nitrate solution 0.5 mol dm -3. (ii) Calculate the number of moles of chromate(vi) ions that has reacted with 1 mole of Pb 2+. ions. (iii) Write the formula of lead(ii) chromate. (iv) Write the ionic equation for the formation of lead(ii) chromate(vi). (d) What can you observed about the height of the precipitate in Figure 1?.. (e) What is your inference based on your answer in (d)?.. 106

107 Chemistry Form 4 Activity 9 : Solve problems involving calculation of quantities of reactants or stoichiometric reactions products in Example 1 : A student prepares copper (II) nitrate by reacting copper (II) oxide with 100 cm mol dm -3 nitric acid. Calculate the mass of copper (II) oxide need to react completely with the acid. [Relative atomic mass: Cu, 64 ; O, 16] Solution : Chemical equation : CuO + 2HNO 3 Cu(NO 3 ) 2 + H 2 O Mole ratio : 1 mole 2 mole 1 mole 1 mole Number of moles of HNO 3 = 1.5 x 100 = 0.15 mol 1000 Mole ratio of CuO : HNO 3 = 1 : 2 Number of mole of CuO = 1 x 0.15 = mole 2 Mass of CuO = x ( ) = 6 g Question : Excess zinc powder is added to react completely with 50 cm of 2.0 mol dm hydrochloric acid. (a) Write an ionic equation for the reaction between zinc and hydrochloric acid. (b) Calculate the number of moles of hydrochloric acid used. (c) Calculate the volume of hydrogen gas liberated at room conditions. 3 1 [Molar volume: 24 dm mol ] 2 Excess of magnesium carbonate powder, MgCO 3, is reacted with 100 cm 3 of a 1 mol dm -3 sulphuric acid H 2 SO 4, What is the mass of magnesium sulphate formed? [Relative atomic mass : Mg =24, O=16, S = 32 ] g of magnesium reacts with excess hydrochloric acid to produce hydrogen gas. Given that the relative molecular mass of H=1, Mg = 24, CI =35.5 and 1 mol of gas occupies 24 dm 3 at room temperature and pressure. Fnd the (a) mass of salt formed (b) volume of gas produced 107

108 Chemistry Form 4 Example 2 : A sample of insoluble lead (II) sulphate is prepared by mixing 50 cm 3 of 1.0 mol dm -3 3 lead (II) nitrate solution and y cm of 1.5 mol dm -3 sulphuric acid. [Relative atomic mass: O, 16 ; S, 32 ; Pb, 207] (a) Calculate the volume, y, of the sulphuric acid needed to react completely with the lead (II) nitrate solution. Solution : Chemical equation : Pb(NO 3 ) 2 + H 2 SO PbSO HNO 3 Mole ratio : 1 mole 1 mole 1 mole 2 mole Number of moles of Pb(NO 3 ) 2 = 1.0 x 50 = 0.05 mol 1000 Mole ratio of Pb(NO 3 ) 2 : H 2 SO 4 = 1 : 1 Number of mole of H 2 SO 4 reacted = 0.05 mol 1.5 x y = 0.05 mole 1000 y = 0.05 x 1000 = cm (b) Calculate the mass of lead (II) sulphate obtained. Solution : Number of mole of PbSO 4 = Number of moles of Pb(NO 3 ) 2 = 0.05 mol Mass of PbSO 4 = 0.05 x ( x 16) g = g Question 3 4. A sample of insoluble silver chloride is prepared by mixing 50cm of 1.0 mol dm -3 silver nitrate 3 3 solution and z cm of 0.5 mol dm sodium chloride solution. [Relative atomic mass: Ag 108; Cl 35.5] (a) Write the chemical equation for the reaction between silver nitrate and sodium chloride. (b) Calculate the volume, z, of the sodium chloride needed to react completely with the silver nitrate solution. (c) Calculate the mass of silver chloride obtained. 108

109 Chemistry Form 4 B. SYNTHESISING QUALITATIVE ANALYSIS OF SALTS Learning Outcomes You should be able to: state examples of salts used in daily life, explain the meaning of salt identify soluble and insoluble salts, describe the preparation of soluble salts, describe the purification of soluble salts by recrystallisation, list physical characteristics of crystals, describe the preparation of insoluble salts, write chemical and ionic equations for reactions used in the preparation of salts, design an activity to prepare a specified salt, construct ionic equations through the continuous variation method solve problems involving calculation of quantities of reactants or products in stoichiometric reactions Activity 10 : Qualitative Analysis 1. Qualtitative analysis of a salt is a chemical technique used to identify the.. that are present in a salt by analysing its. and. properties. 2. Make inferences on the following substances based on their colour: (use formula of substance when writing your answer. Make it is correct!) Colour (solid or solution) Substance or cation or anion Green powder Salt: Cation Blue powder Cation: Brown powder Cation: Black powder Two metal oxides: Yellow powder when hot and white when cold Brown powder when hot and yellow when cold Blue solution Cation: Pale green solution Cation: Brown solution Cation: Solid : White 6 cations : Solution : colourless Solid : White Solution : colourless 4 anions : 3. Complete the following table Salts Solubility in water Colour Insoluble white Copper(II) carbonate Iron(II) sulphate Soluble Brown Lead(II) sulphate Magnesium carbonate Zinc chloride Ammonium carbonate Insoluble Yellow 109

110 Chemistry Form 4 Activity 11 : Confirmatory Tests for gases, Tests For Gases Complete the observation for the confirmatory test for gases Gas Method Diagram Observation Carbon dioxide Bubble the gas produced into lime water Heating Carbonate salts Oxygen Insert a glowing splinter into the test tube Nitrogen dioxide Observe the colour of gas produced. Bring a piece of moist blue litmus paper to the mouth of the test tube Chlorine Observe the colour of the gas. Bring a piece of moist blue litmus paper to the mouth of the test tube Ammonia Hydrogen Dip a glass rod into concentrated hydrochloric acid and bring a drop of acid to the mouth of the test tube /place moist red litmus paper at the mouth of the test tube Bring a lighted splinter to the mouth of the test tube.. Mg + HCl release hydrogen gas 110

111 Chemistry Form 4 Hydrogen chloride Dip a glass rod into concentrated ammonia solution and bring a drop of ammonia to the mouth of test tube Activity 12 : Action of Heat On Carbonate Salts Carbonate salts (except Na + & K + ) decompose on heating giving off carbon dioxide gas and residue metal oxide Metal oxide Colour Copper (II) Black oxide Zinc oxide Hot: yellow ; Cold: White Lead (II) oxide Hot: brown ; Cold: Yellow Iron(III) oxide Brown Lime water turn chalky Activity : Complete the chemical equation and observation for the action of heat on carbonate salt Carbonate salt Potassium carbonate K 2 CO 3, Sodium carbonate Na 2 CO 3 Calcium carbonate Magnesium carbonate Action of heat Not decompose by heat Metal Carbonate metal oxide + carbon dioxide CaCO 3 CaO + CO 2 Observation : White solid formed. Gas liberated turn lime water chalky MgCO Observation :. Aluminium carbonate. Al 2 (CO 3 ) Observation :. Zinc carbonate. ZnCO Observation :. Lead(II) carbonate. PbCO Observation :.. 111

112 Chemistry Form 4 Copper(II) carbonate CuCO Observation :.. Activity 13 : Action of Heat On Nitrate Salts Nitrates Salts - Decompose on heating liberate nitrogen dioxide gas and oxygen gas except NaNO 3 and KNO 3 which liberate oxygen gas only Heat Brown gas turn moist blue litmus to red (NO ) Heat Colourless gas relighted glowing splinter (O 2 ) Activity: Complete the chemical equation and observation for the action of heat on nitrate salt Nitrate salts Action by Heat Metal Nitrate metal nitrite + oxygen Potassium nitrate 2KNO 3 2 KNO 2 + O 2 Sodium nitrate Calcium nitrate Observation : white solid formed, gas released relighted glowing splinter 2NaNO Observation :... Metal Nitrate metal oxide + nitrogen dioxide + oxygen 2Ca(NO 3 ) 2 2CaO + 4NO 2 + O 2 Observation : white solid formed, Brown gas which turns moist blue litmus red released. Another gas released relighted glowing splinter Magnesium nitrate Zinc nitrate Mg(NO 3 ) Observation :... Zn(NO 3 ) Observation :

113 Chemistry Form 4 Lead(II) nitrate Copper(II) nitrate Pb(NO 3 ) Observation :... Cu(NO 3 ) Activity 14 : Confirmatory Tests for Anions, 1. Write the ionic equation for the following reactions. Observation :... CO Dilute acid Effervescence CO 2 Lime water turns milky Ionic equation : Anions Cl - + HNO 3 + AgNO 3 White precipitate Ionic equation : SO HCl + BaCl 2 White precipitate Ionic equation : NO H 2 SO 4 + FeSO 4 + concentrated H 2 SO 4 Brown ring 2. Which anion produce the following observations? a) Add BaCl 2 b) solution + HCl acid Inference : Add AgNO 3 solution + HNO 3 acid Inference : Salt K1 White precipitate formed Salt K2 White precipitate formed 113

114 Chemistry Form 4 c) d) Add FeSO 4 solution + concentrated sulphuric acid Brown ring formed terhasil Inference : Add sulphuric acid Effervescence, Gas bubbles, Gas turn lime water chalky Inference : Salt K3 Salt K4 Activity 15: Reaction of Cations with alkali solution 1. Positive ions are identified by their reactions with a. sodium hydroxide NaOH solution b. Ammonia solution NH 3 2. In these reactions, the cations (positive metal ions) produce different coloured precipitate which may or may not be soluble in excess alkali 5 drops of alkali (NaOH or NH 3 ) Look for precipitate Solution of cations See if Precipitate dissolves Q1 State whether each of the following precipitate is soluble or insoluble in excess alkali. NaOH solution Ammonia Solution NH 3 A little In excess A little In excess Soluble (, X ) Soluble (, X ) Ca 2+ White precipitate No change Zn 2+ White precipitate White precipitate Al 3+ White precipitate White precipitate Pb 2+ White precipitate White precipitate Mg 2+ White precipitate White precipitate Cu 2+ Blue precipitate Blue precipitate Fe 2+ Green precipitate Green precipitate Fe 3+ Brown precipitate Brown precipitate Q2 Which anion produces the following observations? a) Add 5 drops of NaOH solution Add excess NaOH solution Inference 2 : No white precipitate formed, when heated Alkali gas released (ammonia) released Inference 1 White precipitate formed White precipitate Dissolves in excess NaOH solution alkali Inference 3: Salt K5 114 White precipitate does not dissolve in excess NaOH solution

115 Chemistry Form 4 b) No White precipitate formed Inference 4 Add 5 drops of NH 3 solution Salt K6 White precipitate formed Add NH 3 solution in excess White precipitate Dissolve in excess NH 3 White precipitate does not dissolve in Inference5 : Inference 6: Activity 16 : Confirmatory Tests for Fe 2+, Fe 3+, Pb 2+ and NH 4 + (A) The table shows how confirmatory tests are conducted for ammonium ion, NH 4 +, Iron(II) ion, Fe 2+, Iron(III) ion, Fe 3+, and lead(ii) ion, Pb 2+. Complete the confirmatory tests and observation. Cation Name of Reagent Observation 2 Pb 2 Fe Add a few drops of to the test tube containing 2 cm 3 of 2 lead(ii) nitrate solution ( Pb ions) Add 2 cm 3 of distilled water and boil the mixture. Cool the contents using running water from the tap. Add a few drops of to the test tube containing 2 cm 3 of 2 iron(ii) sulphate solution ( Fe ions) precipitate is formed which..in the hot water and is on cooling.. precipitate is formed 3 Fe NH 4 Add a few drops of to the test tube containing 2 cm 3 of 3 iron(iii) sulphate solution ( Fe ions) Add a few drops of to the test tube containing 2 cm 3 of ammonium chloride solution ( NH 4 ions).. solution is formed.. precipitate is formed 115

116 Chemistry Form 4 The diagram below shows the flow chart for the chemical test of Fe 2+ ions and Fe 3+ ions. Test I Solution contains Fe 2+ ions or Fe 3+ ions. Potassium hexacyanoferrate(ii) K 4 Fe(CN) 6 Light blue precipitate Dark blue precipitate Fe 2+ ions Fe 3+ ions Test II Solution contains Fe 2+ ions or Fe 3+ ions. Potassium thiocyanate KSCN No change Blood red solution Fe 2+ ions Fe 3+ ions Based on the flow chart, explain how to differentiate Fe 2+ ions and Fe 3+ ions..... Activity 17 : Qualitative analysis to identify salts (A). Identify the salt S1 The following tests were carried out to identify salt S1. Based on the observations given for each test, state its inference. Finally, identify salt S1 Test Observation Inference 1. Heat S1 strongly in a test tube. Identify any gas liberated. Brown gas and gas relight a glowing splinter liberated. Residue is brown when hot and yellow when cold 2. Dissolve a spatulaful of S1 in distilled water. Divide into four portions and carry out the following tests: (a) add NaOH solution until excess. (b) add NH 3 solution until excess (c) add potassium iodide solution (d) add dilute H 2SO4, followed by FeSO 4 solution. Carefully add about 3 1 cm of concentrated H 2SO 4 Residue dissolve in acid to produce colourless solution White precipitate, dissolve in excess NaOH solution White precipitate, insoluble in excess ammonia solution Yellow precipitate formed Brown ring formed 116

117 Chemistry Form 4 (A). Conclusion for salt S1 :. (B). Identify the salt S2 The following tests were carried out on an aqueous solution of salt S2. Based on the observations given for each test, state its inference. Finally, identify salt S2. Test Observation Inference 3 1. Pour about 2 cm of S2 White precipitate, into a test tube. Add dissolve in excess NaOH solution until excess NaOH solution 3 2. Pour about 2 cm of S2 White precipitate, into a test tube. Add dissolve in excess NH solution until excess ammonia solution Pour about 2 cm of S2 into a test tube. Add dilute HNO 3, followed by silver nitrate, AgNO 3 solution 3 4. Pour about 2 cm of S2 into a test tube. Add dilute HCl solution, then add BaCl 2 solution No change White precipitate (B). Conclusion for salt S2 :.. 117

118 SODIUM CARBONATE SODIUM NITRATE Chemistry Form 4 Activity 18 : plan qualitative analysis to identify anions Rajoo works in a laboratory. He noticed that there are two large bottles. However both the labels have fallen off. He found four labels beside the bottles. i.e Sodium Chloride Solution, Sodium Carbonate Solution, Sodium Sulphate Solution and Sodium Nitrate Solution. So he has to carry out confirmatory test to identify the anion in both the solutions. Complete the graphic organizers describing four tests and their results. The charts can then be used by Rajoo to distinguish which bottle contains which solution. CHART A: SODIUM CARBONATE AND SODIUM NITRATE Result 1 Test 1 Add dilute HNO 3 (or any dilute acid) Result 1 Result 2 Test 2 Add dilute H 2 SO 4 Result 2 followed by solution. Carefully add 1 cm 3 of H 2 SO 4 Result 3 Test 3 Add dilute HNO 3, followed by., solution Result 3 Result 4 Test 4 Add dilute HCl, followed by. solution Result 4 118

119 SODIUM CHLORIDE SODIUM SULPHATE Chemistry Form 4 CHART B: SODIUM CHLORIDE AND SODIUM SULPHATE Result 1 Test 1 Add dilute HNO 3 (or any dilute acid) Result 1 Result 2 Test 2 Add dilute H 2 SO 4 Result 2 followed by solution. Carefully add 1 cm 3 of H 2 SO 4 Result 3 Test 3 Add dilute HNO 3, followed by., solution Result 3 Result 4 Test 4 Add dilute HCl, followed by. solution Result 4 119

120 Chemistry Form 4 CHAPTER 9 : MANUFACTURED SUBSTANCES IN INDUSTRY A : SULPHURIC ACID Learning Outcomes You should be able to: list uses of sulphuric acid explain industrial process in the manufacture of sulphuric acid explain that sulphur dioxide causes environmental pollution. Activity 1 : SULPHURIC ACID 1. Sulphuric acid is manufactured through the.process. 2. Contact Process consists of three stages: (Complete the table below) Stage 1 Stage 2 Stage 3 Preparation of (a) gas Chemical equation : S + O 2 SO 2 Conversion of sulphur dioxide to sulphur trioxide Chemical equation : (b) Catalyst : (c).. Temperature : (d).. o C Pressure : (e).. atm Production of sulphuric acid Chemical equation : (f) + H 2 SO 4.. (g). + H 2 O. 3. State six uses of sulphuric acid. i).. ii).. iii).... iv). v) vi) gas from the burning of product manufactured from sulphuric acid can cause disease and rain. 5. Figure 1 below shows the waste product from a factory which affect the quality of the environment. 120

121 Chemistry Form 4 Figure 1 a) By referring to the Figure 1 above, state the following, i) Types of waste products and their sources. ii) How acid rain is formed and its effect. Formation of acid rain:.. Effects on environment:.. iii) How does the toxic waste affect the environment and its effect B : AMMONIA Learning Outcomes... You should be able to: list uses of ammonia state the properties of ammonia explain the industrial process in the manufacture of ammonia design an activity to prepare ammonium fertilizer. Activity 2 : AMMONIA 1. Ammonia is manufactured through the Haber Process by combining gas and.gas. 2. (i). The reaction can be represented by the chemical equation (ii) State the condition necessary to produce ammonia. Catalyst : (a).. 121

122 Chemistry Form 4 Temperature : (b). Pressure : (c) Ratio N 2 :H 2 : (d) 3. The following statements refer to the uses of ammonia. Fill in the blank with the correct words. (a) To manufacture.. such as ammonium sulphate and ammonium nitrate. The chemical equation for producing ammonium sulphate is given by (b) Ammonia is used as raw material to produce. in the Ostwald Process. (c) Ammonia is also used as an alkali to prevent the of latex. 4. Listed below are three properties of ammonia. Fill in the blank according to the aspect given. (a) Colour: Ammonia is a.. gas. (b) Solubility: Ammonia is very in water. (a) Smell : Ammonia has a smell. (b) Ammonia dissolves in water to produce an. solution. 5. Ammonium fertiliser can be prepared in the laboratory by adding ammonia solution and certain acids as shown in the table below. Neutralisation reactions Alkali Acid Aqueous + Phosphoric ammonia acid Aqueous + Nitric ammonia acid Aqueous + Sulphuric ammonia acid Name of ammonium salt (fertiliser) Ammonium phosphate (a) Formula:.. Ammonium nitrate (b) Formula:.. Ammonium sulphate (c ) Formula:. (i) Calculate the percentage of nitrogen found in each of the ammonium fertilisers. [Relative atomic mass: H = 1; N = 14; O = 16; P = 31; S = 32] (ii) From the calculations in (b)(ii), deduce the type of ammonium compound that is most suitable for use as a nitrogenous fertiliser. Give reasons for your answer. 122

123 Chemistry Form 4. C : ALLOY Learning Outcomes You should be able to: relate the arrangement of atoms in metals to their ductile and malleable properties state the meaning of alloy state the aim of making alloys list examples of alloys list compositions and properties of alloys relate the arrangement of atoms in alloys to their strength and hardness relate properties of alloys to their uses. Activity 4: ALLOY 1. What is alloy? Alloy is a...of a pure metal with...in...quantities Figure 2 2. A pure metals contains atoms of the same size arranged in a regular and orderly manner. Pure metal are.. and. because the layers of atom when external force is applied on them. 3. In an alloy, the foreign metal atoms....arrangement of metal atoms and the layers of metal atoms are prevented from...over each other easily. 4. Complete the sequences by drawing the arrangement of atoms in the box below. + Pure metal Another pure 5. Three aims of alloying metal a pure metal are : alloy a. to increase the. and.. of metal. b. to prevent or rusting. c. to improve the. of metal surface. 123