Farr High School. NATIONAL 5 CHEMISTRY Unit 1 Chemical Changes and Structure. Exam Questions (UPDATED MAY 2017)

Transcription

1 Farr High School NATIONAL 5 CHEMISTRY Unit Chemical Changes and Structure Exam Questions (UPDATED MAY 207)

2 Rates of Reaction 202 Int2 2. Rapid inflation of airbags in cars is caused by the production of nitrogen gas. The graph gives information on the volume of gas produced over 30 microseconds. Calculate the average rate of reaction, in litres per microsecond, between 2 and 0 microseconds. 2

3 202 Int 2 2. Egg shells are made up mainly of calcium carbonate. A pupil carried out an experiment to react egg shells with dilute hydrochloric acid. A gas was produced. The volume of gas produced during the reaction was measured. 2 Plot these results as a line graph. 20 H 3. Chloromethane, CH 3 Cl, can be produced by reacting methanol solution with dilute hydrochloric acid using a solution of zinc chloride as a catalyst. The graph shows how the concentration of the hydrochloric acid changed over a period of time when the reaction was carried out at 20 C. Calculate the average rate, in mol l min, in the first 400 minutes. 3

4 4. Copper(II) carbonate reacts with dilute hydrochloric acid as shown. 202 H 2 A student used the apparatus shown below to follow the progress of the reaction. The experiment was carried out using 0 50 g samples of both pure and impure copper(ii) carbonate. The graph below shows the results obtained. For the sample of pure copper(ii) carbonate, calculate the average reaction rate, in g s -, over the first 0 seconds. 4

5 5. Excess marble chips (calcium carbonate) were added to 25 cm3 of hydrochloric acid, concentration 2 mol l. 203 H 5MC Which of the following measurements, taken at regular intervals and plotted against time, would give the graph shown above? A Temperature B Volume of gas produced C ph of solution D Mass of the beaker and contents 2007 H 4 MC 6. The graph shows the variation of concentration of a reactant with time as a reaction proceeds. What is the average reaction rate during the first 20 s? A mol l s B mol l s C mol l s D mol l s 5

6 7. The following results were obtained in the reaction between marble chips and dilute hydrochloric acid H 5MC What is the average rate of production of carbon dioxide, in cm 3 min, between 2 and 8 minutes? A 5 B 26 C 30 D Int2 2MC 8. During the first 20 seconds of a chemical reaction, 5 0 cm 3 of gas were given off. The average rate of the reaction, in cm 3 s, during the first 20 seconds is A 20 0 B 5 0 C 4 0 D Int2 4b 9. Research is being carried out into making chemicals that can be used to help relieve the side effects of chemotherapy. Part of the process is shown. catalyst chemical A + hydrogen chemical B As the reaction proceeds the hydrogen is used up and the pressure decreases. (a) Draw a line graph showing the decrease in pressure as time proceeds. 2 (b) Using your graph, at what time did the reaction finish? (c) Calculate the average rate of the reaction, in bar min, between 0 and 20 minutes. 6

7 2008 Int2 9c 0. A student investigated the effect of temperature on the rate of starch formation. The results are shown. (a) Plot these results as a line graph. (b) At 32 C the relative rate was 0.025s. Use this rate to calculate the reaction time, in seconds, at 32 C. 204 N5 MC. In a reaction, 60 cm 3 of hydrogen gas was collected in 20 s. What is the average rate of reaction, in cm 3 s, over this time? A 60/20 B 20/60 C /60 D /20 7

8 2. A student reacted acidified potassium permanganate solution with oxalic acid, C 2 H 2 O N5 6 2MnO 4 (aq) + 5C 2 H 2 O 4 (aq) + 6H + (aq) 2Mn 2+ (aq) + 0CO 2 (g) + 8H 2 O(l) Using your knowledge of chemistry, comment on how the student could have determined the rate of the reaction Ethyne is the first member of the alkyne family. It can be produced by the reaction of calcium carbide with water. The equation for this reaction is 205 N5 CaC 2 (s) + 2H 2 O(l) C 2 H 2 (g) + Ca(OH) 2 (aq) (a) The table shows the results obtained in an experiment carried out to measure the volume of ethyne gas produced. Time (s) Volume of ethyne (cm 3 ) Calculate the average rate of reaction between 60 and 90 seconds. Your answer must include the appropriate unit. Show your working clearly. 3 (b) Draw a line graph of the results. Use appropriate scales to fill most of the graph paper N5 MC 2 4. The table shows the times taken for 0 5 g of magnesium to react completely with acid under different conditions. Acid concentration (mol l - ) Temperature ( C) Reaction time (s) The time for 0 5 g of magnesium to react completely with 0 2 mol l acid at 25 C will be A less than 0 s B between 0 s and 20 s C between 20 s and 60 s D more than 80 s. 8

9 206 N Hydrogen gas can be produced in the laboratory by adding a metal to dilute acid. Heat energy is also produced in the reaction. (a) State the term used to describe all chemical reactions that release heat energy. (b) A student measured the volume of hydrogen gas produced when zinc lumps were added to dilute hydrochloric acid. Time (s) Volume of hydrogen (cm 3 ) (i) Calculate the average rate of reaction, in cm 3 s, between 0 and 30 seconds. Show your working clearly. 2 (ii) Estimate the time taken, in seconds, for the reaction to finish. (iii) The student repeated the experiment using the same mass of zinc. State the effect on the rate of the reaction if zinc powder was used instead of lumps. 9

10 Atomic structure and bonding related to properties of materials. (a) Complete the table to match up each type of bonding and structure with its properties. 20 Int2 2 (b) A section of a covalent network compound is shown below. Write the formula for this covalent network compound. 0

11 2. I nformation on some two-element molecules is shown in the tab le. 2. Information on some two-element molecules is shown in the table. N am e Formula Shape of m olecule 20 Int 2 2 hydrogen fluoride H F water H 2 O ammonia NH 3 (a) Complete (a) the Complete table to the show table the to shape show of the a shape molecule of of a molecule ammonia. of ammonia. (b) The hydrogen fluoride molecule can be represented as: Showing all outer electrons, draw a similar diagram to represent a molecule of water, H 2 O.

12 20 Int Write the formula for ruthenium(ii) chloride. 4. Fluoride prevents tooth decay by replacing the hydroxide ions of calcium hydroxyapatite with fluoride ions to form hard wearing calcium fluoroapatite. 20 Int2 5 Write the formula for calcium fluoroapatite. 5. Dishwasher tablets contain many different types of chemicals. 203 Int2 6 Phosphate ions, present in some types of dishwasher tablets, react with calcium ions in water forming calcium phosphate. Write the formula for calcium phosphate. 6. The table shows information about some useful compounds. 203 SG Name compound Y. 2

13 203 Int Tritium is a naturally occurring isotope of hydrogen. It can be represented as (a) Complete the table to show the number of particles in an atom of tritium. (b) Hydrogen has three isotopes. The relative atomic mass of hydrogen is. Which isotope of hydrogen is the most abundant? 8. The nuclide notation for an isotope of hydrogen is An isotope of copper has atomic number 29 and mass number SG 0 (a) (i) Write the nuclide notation for this isotope of copper. (ii) How many neutrons are present in this isotope of copper? (b) A sample of copper was found to contain equal amounts of two isotopes. One has mass number 63 and the other has mass number 65. What is the relative atomic mass of this sample of copper? 3

14 203 SG 6 9. Metals can be extracted from their ores by different methods. Mercury can be extracted from the ore cinnabar, HgS. Write the formula for the mercury ion in cinnabar. 0. Nitrogen trifluoride, NF 3, is used in the manufacture of plasma screens. 203 SG 7 (a) (b) Draw a diagram showing all outer electrons to represent a molecule of nitrogen trifluoride. The atoms in nitrogen trifluoride are held together by covalent bonds.. Hydrogen gas is made up of diatomic molecules. 202 SG 3 Draw a diagram to show how the electrons are arranged in a molecule of hydrogen, H SG 5 2. Ammonium phosphate is used as a fertiliser. Write the ionic formula for ammonium phosphate. 3. A student investigated how the concentration of sodium chloride in water affected the freezing point. 202 SG 8 (a) What type of bond is broken in sodium chloride when it dissolves in water? (b) The table shows information about the freezing point of different sodium chloride solutions. Describe the relationship between the concentration and freezing point. (c) Predict the freezing point, in o C, of a 0 55 mol/l sodium chloride solution. 4

15 20 SG 2 4. Ethanol, for alcoholic drinks, can be made from glucose. The table below shows the relationship between the percentage of ethanol and the density of alcoholic drinks. (a) Write a general statement describing how the percentage of ethanol affects the density of the alcoholic drink. (b) The density of a particular brand of alcoholic drink is g cm -3. Predict the percentage of ethanol in this alcoholic drink. 5. Heptane can be cracked as shown. 20 SG 6 Aluminium oxide is used as a catalyst to speed up the reaction. Write the formula for aluminium oxide. 5

16 6. A student set up the following experiment to electrolyse cobalt chloride solution. 20 SG 8 The formula for cobalt chloride is CoCl 2. What is the charge on the cobalt ion in CoCl 2? 204 N5 MC 2 7. Molecules in which four different atoms are attached to a carbon atom are said to be chiral. Which of the following molecules is chiral? 6

17 204 N5 8. In 9, Ernest Rutherford carried out an experiment to confirm the structure of the atom. In this experiment, he fired positive particles at a very thin layer of gold foil. Most of the particles passed straight through but a small number of the positively charged particles were deflected. (a) What caused some of the positive particles to be deflected in this experiment? (b) Gold is the heaviest element to have only one naturally occurring isotope. The isotope has a mass number of 97. (i) Complete the table to show the number of each type of particle in this gold atom. You may wish to use the data booklet to help you. (ii) Most elements have more than one isotope. State what is meant by the term isotope. 204 N (a) The properties of a substance depend on its type of bonding and structure. There are four types of bonding and structure. Discrete covalent molecular covalent network ionic lattice metallic lattice Complete the table to match up each type of bonding and structure with its properties. Type of bonding and structure Properties do not conduct electricity and have high melting points have high melting points and conduct electricity when liquid but not when solid conduct electricity when solid and have a wide range of melting points do not conduct electricity and have low melting points 2 7

18 (b) Graphene is a substance made of a single layer of carbon atoms. Graphene can conduct electricity. Suggest what this indicates about some of the electrons in graphene. 20. An atom has 26 protons, 26 electrons and 30 neutrons. The atom has 205 N5 MC A atomic number 26, mass number 56 B atomic number 56, mass number 30 C atomic number 30, mass number 26 D atomic number 52, mass number N5 MC 2 2. The table shows the numbers of protons, electrons and neutrons in four particles, W, X, Y and Z. Particle Protons Electrons Neutrons W X 2 Y Z Which pair of particles are isotopes? A W and X B W and Y C X and Y D Y and Z 205 N5 MC Which of the following particles contains a different number of electrons from the others? You may wish to use the data booklet to help you. A Cl B S 2 C Ar D Na + 8

19 205 N5 MC Which of the following diagrams shows the apparatus which would allow a soluble gas to be removed from a mixture of gases? 205 N5 MC Which of the following diagrams could be used to represent the structure of a covalent network? 9

20 25. The table contains information about calcium and calcium chloride. 205 N5 MC 7 Melting point ( C) Density (g cm -3 ) Calcium Calcium chloride When molten calcium chloride is electrolysed at 800 ºC the calcium appears as a A solid at the bottom of the molten calcium chloride B liquid at the bottom of the molten calcium chloride C solid on the surface of the molten calcium chloride D liquid on the surface of the molten calcium chloride 205 N Some sources of methane gas contain hydrogen sulfide, H 2 S. Draw a diagram, showing all outer electrons, to represent a molecule of hydrogen sulfide, H 2 S. 205 N5 27. Electrons can be removed from all atoms. The energy required to do this is called the ionisation energy. The first ionisation energy for an element is defined as the energy required to remove one mole of electrons from one mole of atoms, in the gaseous state. The equation for the first ionisation energy of chlorine is Cl(g) Cl + (g) + e (a) State the electron arrangement for the Cl + ion. You may wish to use the data booklet to help you. (b) Write the equation for the first ionisation energy of magnesium. (c) Information on the first ionisation energy of some elements is given in the table. Element First ionisation energy (kj mol - ) Lithium 526 Fluorine 690 Sodium 502 Chlorine 260 Potassium 425 Bromine 50 Describe the trend in the first ionisation energy going down a group in the Periodic Table. 20

21 28. Titanium is the tenth most commonly occurring element in the Earth s crust. 205 N5 4 The first step in the extraction of titanium from impure titanium oxide involves the conversion of titanium oxide into titanium(iv) chloride. TiO 2 + 2Cl 2 + 2C TiCl 4 + 2X (a) Identify X. (b) Titanium(IV) chloride is a liquid at room temperature and does not conduct electricity. Suggest the type of bonding that is present in titanium(iv) chloride. 206 N5 MC 29. When solid sodium chloride dissolves in water, a solution containing sodium ions and chloride ions is formed. Which of the following equations correctly shows the state symbols for this process? A NaCl(s) + H 2 O(l) Na + (l) + Cl (l) B NaCl(s) + H 2 O(aq) Na + (aq) + Cl (aq) C NaCl(aq) + H 2 O(l) Na + (aq) + Cl (aq) D NaCl(s) + H 2 O(l) Na + (aq) + Cl (aq) 30. When an atom X of an element in Group reacts to become X N5 MC 3 A the mass number of X decreases B the atomic number of X increases C the charge of the nucleus increases D the number of occupied energy levels decreases 3. Which of the following does not contain covalent bonds? 206 N5 MC 4 A Sulfur B Copper C Oxygen D Hydrogen 32. Which of the following structures is never found in compounds? 206 N5 MC 5 A Ionic B Monatomic C Covalent network D Covalent molecular 2

22 33. Which line in the table shows the properties of an ionic substance? 206 N5 MC Elements are made up of atoms. 206 N5 (a) Complete the tables to show the missing information. (i) (ii) (b) A sample of nitrogen was found to contain equal amounts of two isotopes. One isotope has mass number 4 and the other has mass number 5. What is the relative atomic mass of this sample of nitrogen? (c) Nitrogen can form bonds with other elements. The diagram shows the shape of a molecule of ammonia (NH 3 ). State the name used to describe the shape of a molecule of ammonia. 22

23 35. Read the passage and answer the questions that follow. 206 N5 5 Gold a very useful metal Gold has been associated with wealth since before the first gold coins were minted in Lydia (modern Turkey) about 550 BC. It does not react with water, air, alkalis and almost all acids. Gold only has one naturally occurring isotope with mass 97. As an element it has many uses in the modern world. gram of gold can be beaten into a gold film covering one square metre and thin coatings of gold are used as lubricants in aerospace applications. Gold electroplating can be used to coat electrical connectors and printed circuit boards. Chemists have recently discovered that gold nanoparticles make superb catalysts for many reactions such as the conversion of alcohols into aldehydes and ketones. It can also be used as a catalyst for removing trace carbon monoxide from gases. In this reaction carbon monoxide reacts with oxygen to form carbon dioxide. Gold nanorods can be grown from a dilute solution of auric acid and are used in the treatment of some forms of cancer. Adapted from Education in Chemistry, Volume 45, November 2008 (a) Suggest a reason why gold was used in the first coins minted. (b) Calculate the number of neutrons present in the naturally occurring isotope of gold. You may wish to use the data booklet to help you. (c) (i) Write an equation, using symbols and formulae, to show the reaction for removing trace carbon monoxide from gases. There is no need to balance this equation. (ii) State the role of gold in this reaction. 23

24 Formulae and reaction quantities. Rapid inflation of airbags in cars is caused by the production of nitrogen gas. In some types of airbag, electrical energy causes sodium azide, NaN 3, to decompose producing sodium metal and nitrogen gas. Write a formula equation for this reaction. 202 Int Int Rust, iron(iii) oxide, that forms on cars can be treated using rust remover which contains phosphoric acid. When painted on, rust remover changes iron(iii) oxide into iron(iii) phosphate. The rust remover contains 250 cm 3 of 2 mol l - phosphoric acid. (a) Calculate the number of moles of phosphoric acid in the rust remover. (b) Using your answer in part (i), calculate the mass of iron(iii) oxide, in grams, that will be removed by 250 cm 3 of 2 mol l - phosphoric acid SG 7 3. Urea reacts with water, breaking down to form carbon dioxide and ammonia. Calculate the mass of ammonia produced, in grams, when 90 g of urea breaks down. 2 24

25 4. Hydrogen peroxide is a useful bleaching agent and is contained in many hair dyes. Over time, the hair dye becomes less effective as the hydrogen peroxide decomposes forming water and oxygen. 20 Int2 3 The equation for the decomposition of hydrogen peroxide is: (a) Balance this equation. (b) When 34g of hydrogen peroxide decomposes, 2 litres of oxygen is produced. Calculate the volume of oxygen, in litres, produced when 7g of hydrogen peroxide decomposes. 5. Metal salts can be produced by different methods. Lead(II) iodide can be produced by reacting lead(ii) nitrate solution with sodium iodide solution. The equation for this reaction is: 20 SG 20 (a) Balance the above equation. (b) Potassium sulphate can be produced by titrating potassium hydroxide solution with dilute sulphuric acid. The average volume of sulphuric acid used in the titration is 20 cm 3. Calculate the number of moles of sulphuric acid used. SG Potassium hydroxide reacts with sulphuric acid to form potassium sulphate, which can be used as a fertiliser. Balance the above equation. 25

26 202 SG 7 7. A solution of 0 mol l - hydrochloric acid has a ph of. Calculate the number of moles of hydrochloric acid in 50cm 3 of 0 mol l - hydrochloric acid solution. 8. Aluminium is extracted from the ore bauxite. The composition of a 250 g magnet is shown. 202 SG 2 (a) (b) Calculate the mass, in grams, of aluminium in the magnet. Show your working clearly. Using your answer to (a), calculate the number of moles of aluminium in the magnet. Show your working clearly. 9. Nitrogen trifluoride, NF 3, is used in the manufacture of plasma screens. The equation for the formation of nitrogen trifluoride, NF 3, is: 203 SG 7 Calculate the mass, in grams, of nitrogen trifluoride produced from 7 g of nitrogen. 2 Show your working clearly. 0. A student investigated the reaction between dilute sulphuric acid and sodium carbonate. 203 SG 8 A student carried out an experiment to determine the concentration of sodium carbonate solution by titration with sulphuric acid. The results showed that 20cm 3 of sulphuric acid was required to neutralise the sodium carbonate solution. Calculate the number of moles of sulphuric acid in this volume. 26

27 . What is the charge on the zinc ion in the compound zinc phosphate Zn 3 (PO 4 ) 2? 204 N5 MC 3 A 2+ B 3+ C 2 D 3 2. Fe 2 O 3 + x CO y Fe + 3CO 2 This equation will be balanced when 204 N5 MC 4 A x = and y = 2 B x = 2 and y = 2 C x = 3 and y = 2 D x = 2 and y = Read the passage below and answer the questions that follow. Potassium - The Super Element Potassium is an essential element for almost all living things. The human body requires a regular intake of potassium because humans have no mechanism for storing it. Foods rich in potassium include raisins and almonds. Raisins contain 0 86 g of potassium in every 00 g. 204 N5 3 Naturally occurring salts of potassium such as saltpetre (potassium nitrate) and potash (potassium carbonate) have been known for centuries. Potassium salts are used as fertilisers. Potassium was first isolated by Humphry Davy in 807. Davy observed that when potassium was added to water it formed globules which skimmed about on the surface, burning with a coloured flame and forming an alkaline solution. (a) State why the human body requires a regular intake of potassium. (b) Calculate the number of moles of potassium in 00 g of raisins. Show your working clearly. 2 (c) State the colour of the flame which would be seen when potassium burns. You may wish to use the data booklet to help you. (d) Write the ionic formula for saltpetre. 4. What is the charge on the chromium ion in CrCl 3? 205 N5 MC 6 A + B - C 3+ D 3-27

28 5. x Al(s) + y Br 2 (l) z AlBr 3 (s) This equation will be balanced when 205 N5 MC 8 A x =, y = 2 and z = A x = 2, y = 3 and z = 2 A x = 3, y = 2 and z = 3 A x = 4, y = 3 and z = mol of a gas has a mass of 2.8 g. Which of the following could be the molecular formula for the gas? 205 N5 MC 9 A SO 2 B CO C CO 2 D NH 3 7. Read the passage below and answer the questions that follow. Clean coal technology comes a step closer 205 N5 6 It is claimed a process called Coal-Direct Chemical Looping (CDCL) is able to release energy from coal while capturing 99% of the carbon dioxide emitted. CDCL works by extracting the energy from coal using a reaction other than combustion. A mixture of powdered coal and beads of iron(iii) oxide is heated inside a metal cylinder. Carbon in the coal and oxygen from the beads react to form carbon dioxide which can be captured for recycling or stored. This reaction gives off heat energy that could be used to heat water in order to drive electricityproducing steam turbines. Adapted from Focus: Science and Technology, April 203 (a) The CDCL process produced 300 tonnes of carbon dioxide. Calculate the mass, in tonnes, of carbon dioxide released into the atmosphere. (b) Write the ionic formula for the iron compound used in CDCL. (c) State the term used to describe all chemical reactions that release heat energy. 28

29 205 N A student was asked to carry out an experiment to determine the concentration of a copper(ii) sulfate solution. Part of the work card used is shown. (a) Suggest how the student could have evaporated the solution to dryness. (b) The student found that the 00 cm 3 solution contained 3 9 g of copper(ii) sulfate, CuSO 4. Calculate the concentration of the solution in mol l. Show your working clearly. 9. What is the name of the compound with the formula Ag 2 O? 206 N5 MC 7 A Silver(I) oxide B Silver(II) oxide C Silver(III) oxide D Silver(IV) oxide 20. Another student reacted aluminium with dilute nitric acid. 206 N5 3 2Al(s) + 6HNO 3 (aq) 2Al(NO 3 ) 3 (aq) + 3H 2 (g) mole of hydrogen gas has a volume of 24 litres. Calculate the volume of hydrogen gas, in litres, produced when 0 0 moles of aluminium react with dilute nitric acid. Show your working clearly N In the production of the fertiliser ammonium phosphate, phosphoric acid (H 3 PO 4 ) reacts with ammonium hydroxide as shown. H 3 PO 4 (aq) + NH 4 OH(aq) (NH 4 ) 3 PO 4 (aq) + H 2 O(l) Balance this equation. 206 N Oxalic acid is found naturally in rhubarb. A piece of rhubarb was found to contain 8 g of oxalic acid. Calculate the number of moles of oxalic acid contained in the piece of rhubarb. (Formula mass of oxalic acid = 90) 29

30 23. Mercury can be extracted from the ore cinnabar, HgS. Calculate the percentage by mass of mercury in cinnabar C Anglesite is an ore containing lead(ii) sulphate, PbSO 4. Calculate the percentage by mass of lead in anglesite C Calculate the percentage by mass of lead in galena, PbS N Iron can be extracted from its ore haematite, Fe 2 O 3, in a blast furnace. Calculate the percentage by mass of iron in haematite. Show your working clearly N Calculate the percentage mass of silicon in andalusite, Al 2 SiO 5. Show your working clearly. 3 30

31 Acids and Bases 20 Int2 5. Fizzy drinks contain acids. These acids can attack the compound calcium hydroxyapatite which is found in tooth enamel. The equation for the reaction is: What will happen to the ph as the tooth enamel is attacked by the acids? 2. A student carried out the following experiment. 202 Int2 3 The equation for the reaction is (a) Rewrite the equation showing only the ions which react. (b) What term is used to describe the ions which do not react? 20 SG 4 3. When sulphur dioxide dissolves in water in the atmosphere acid rain is produced. 4. Metal salts can be produced by different methods. The salt copper(ii) nitrate can be produced as shown. 20 SG 20 Name substance X. 3

32 202 SG 5 5. Potassium hydroxide reacts with sulphuric acid to form potassium sulphate, which can be used as a fertiliser. Name the type of chemical reaction taking place. 6. A solution of 0 mol l - hydrochloric acid has a ph of. 202 SG 7 (a) What colour would universal indicator turn when added to a solution of hydrochloric acid? (b) Starting at ph, draw a line to show how the ph of this acid changes when diluted with water Int2 9MC 7. Which of the following increases when hydrochloric acid is diluted with water? A Rate of reaction with magnesium B Concentration of H+ ions C Electrical conductivity D ph 2007 Int2 20MC 8. Which of the following statements describes the concentrations of H + (aq) and OH (aq) ions in pure water? A The concentrations of H + (aq) and OH (aq) ions are equal. B The concentrations of H + (aq) and OH (aq) ions are zero. C The concentration of H + (aq) ions is greater than the concentration of OH (aq) ions. D The concentration of OH (aq) ions is greater than the concentration of H + (aq)ions Int2 23MC 9. When hydrochloric acid with a ph of 3 is diluted with water to give a solution with a ph of 6, the concentration of A H + (aq) ions decreases B OH (aq) ions decreases C H + (aq) ions and the concentration of OH (aq) ions become equal D H + (aq) ions and the concentration of OH (aq) ions remains unchanged 32

33 2006 Int2 24MC 0. Which of the following sodium compounds is a base? A sodium carbonate B sodium chloride C sodium nitrate D sodium sulphate 2006 Int2 2c. Ammonia gas NH 3 (g), can be dissolved Hydrogen chloride gas HCl(g), can be in water to form concentrated dissolved in water to form concentrated ammonia solution. hydrochloric acid. If both bottles are placed next to each other in a fume cupboard and the stoppers removed, both liquids evaporate and a white cloud is formed where the two gases meet. (a) State the colour of the ph paper at (i) X and (ii) Y. (b) The white cloud appears because the gases react to form a salt. Name the salt. 33

34 204 N Sodium carbonate solution can be added to the water in swimming pools to neutralise the acidic effects of chlorine. A student carried out a titration experiment to determine the concentration of a sodium carbonate solution. (a) Using the results in the table, calculate the average volume, in cm 3, of hydrochloric acid required to neutralise the sodium carbonate solution. (b) The equation for the reaction is 2HCl + Na 2 CO 3 2NaCl + CO 2 + H 2 O Using your answer from part (a) calculate the concentration, in mol l -, of the sodium carbonate solution. Show your working clearly An acidic solution contains 204 N5 MC 5 A only hydrogen ions B only hydroxide ions C more hydrogen ions than hydroxide ions D more hydroxide ions than hydrogen ions. 4. Which of the following oxides, when shaken with water, would give an alkaline solution? 204 N5 MC 6 A Calcium oxide B Nickel oxide C Nitrogen dioxide D Sulfur dioxide 34

35 5. Which of the following compounds is not a salt? 204 N5 MC 7 A Calcium nitrate B Sodium chloride C Potassium sulfate D Magnesium hydroxide 6. H + (aq) + NO 3 (aq) + K + (aq) + OH (aq) K + (aq) + NO 3 (aq) + H 2 O(l) The spectator ions present in the reaction above are 204 N5 MC 8 A K + (aq) and NO 3 (aq) B K + (aq) and H + (aq) C OH (aq) and NO 3 (aq) D H + (aq) and OH (aq) 205 N5 MC 0 7. Which of the following oxides, when shaken with water, would leave the ph unchanged? You may wish to use the data booklet to help you. A Carbon dioxide B Copper oxide C Sodium oxide D Sulfur dioxide 8. Which compound would not neutralise hydrochloric acid? 205 N5 MC A Sodium carbonate B Sodium chloride C Sodium hydroxide D Sodium oxide 205 N Some sources of methane gas contain hydrogen sulfide, H 2 S. (a) If hydrogen sulfide is not removed before methane gas is burned, sulfur dioxide is formed. When sulfur dioxide dissolves in water in the atmosphere, acid rain is produced. (b) In industry, calcium oxide is reacted with sulfur dioxide to reduce the volume of sulfur dioxide released into the atmosphere. Explain why calcium oxide is able to reduce the volume of sulfur dioxide gas released. 35

36 205 N Vitamin C is found in fruits and vegetables. Using iodine solution, a student carried out titrations to determine the concentration of vitamin C in orange juice. (a) Calculate the average volume, in cm 3, that should be used in calculating the concentration of vitamin C. (b) The equation for the reaction is C 6 H 8 O 6 (aq) + I 2 (aq) C 6 H 6 O 6 (aq) + 2HI(aq) vitamin C Calculate the concentration, in mol l, of vitamin C in the orange juice. Show your working clearly N5 MC 8 2. An element was burned in air. The product was added to water, producing a solution with a ph less than 7. The element could be A tin B zinc C sulfur D sodium 36

37 22. Betanin can be used as an indicator in a neutralisation reaction. The ph range at which some indicators change colour is shown. Indicator ph range of colour change Methyl orange 3.2 to 4.4 Litmus 5.0 to 8.0 Phenolphthalein 8.2 to 0.0 betanin 9.0 to N5 2 The indicator used in a neutralisation reaction depends on the ph at the end point. The table below shows the end point of neutralisation reactions using different types of acid and base. Type of acid Type of base ph at the end point Strong Strong 7 Strong Weak Below 7 Weak Strong Below 7 (a) Betanin can be used to indicate the end point in the reaction between oxalic acid and sodium hydroxide solution. State the type of acid and the type of base used in this reaction. (b) A student carried out a titration experiment to determine the concentration of a sodium hydroxide solution. Using the results in the table, calculate the average volume, in cm 3, of oxalic acid required to neutralise the sodium hydroxide solution. 37