Answers for UNIT ONE NAT 5 Flash Cards

Answers for UNIT ONE NAT 5 Flash Cards 1. (a) rate increases (b) rate increases (c) rate increases (d) rate increases 2. Average rate = change in property / change in time Where property = concentration, volume, mass i.e. Average rate = ΔC/Δt OR = ΔV/Δt OR = Δm /Δt 3. At 2 hrs concentration = 20mg/l; at 6hrs = 10mg/l Average rate = ΔC/Δt = 20 10 / 6-2 = 10/4 = 2.5 mg/l/hr 4. At 40s = 56cm 3 ; at 60s = 73cm 3 Average rate = ΔV/Δt = 73 56 / 60 40 = 6.45cm 3 /s 5. (a) alkali metals (b) halogens (c) Noble gases 6. (a) very reactive metals (b) very reactive non-metals (c) unreactive g non-metal gases 7. transition metals 8. (a) two atoms joined together by a covalent bond. (b) Hydrogen (H 2 ), Oxygen (O 2 ), Nitrogen (N 2 ), Fluorine (F 2 ), Chlorine (Cl 2 ), Bromine (Br 2 ), Iodine (I 2 ) 9. An element contains only one type of atom. 10. (a) Only two: Bromine (non-metal) and mercury (metal) (b) Only eleven: Hydrogen, nitrogen, oxygen, fluorine, chlorine and all of group 8(0) 1

11. *. * neutron nucleus electron * proton in energy level 12. Particle Mass (amu) Charge Position in Atom Proton 1 + In nucleus Electron 0 - Outside nucleus Neutron 1 0 Inside nucleus 13.(a) An atom contains equal numbers of positive protons and negative electrons. (b) Positive; as the nucleus contains + protons and neutral neutron making the overall charge positive. 14. (a) The atomic number = the umber of protons (b) In the data booklet in the periodic table. 15.(a) Mass number = number of protons + number of neutrons (b) No, the mass number has to be calculated by adding together the number of neutrons and protons in an individual isotope of an element. 16. (a) Calcium-40; p = 20; e= 20; n = 20; 40 20 Ca (b) Carbon-13; p = 6; e = 6; n = 7; 13 6 C (c) Chlorine-35; p = 17; e = 17; n = 18; 35 17 Cl 2

17. The electronic configuration or arrangement shows how the electrons are arranged in an atom. 18. (a) 2 (b) 8 (c) 8 (18) 19(a) sodium = 2,8,1 (b) Fluorine = 2,7 (c) Calcium = 2,8,8,2 20. They have the same number of OUTER electrons. 21. The OUTER energy level. 22. They have the same number of outer electrons or they are in the same group in the periodic table. 23. (a) A and B (are in the same group) (b) (i) D (noble gas) (ii) E (group 7 chlorine) (iii) A or B (group 1 alkali metal) 24. An ion is a charged particle formed when an atom loses or gains electrons. 25. (a) Metal atoms lose electrons to gain a stable electron arrangement. (b) Metals form a positive ion. 26. (a) Non- metal atoms gain electrons to gain a stable electron Arrangement. (b) Non-metals form a negative ion. 3

27. (a) 23 11Na + = 1+ ion so the metal sodium has lost one electron. P = 11 e = 10 (2,8) n = 12 (b) 32 16S 2- = 2- ion so the non-metal sulphur has gained two electrons. P = 16 e = 18 (2,8,8) n = 16 28. Isotopes are atoms of the same element which have the same atomic number but a different mass number. 29. (a) The relative atomic mass is the average mass of all the isotopes in an element. The mass is calculated relative to carbon-12. (b) The relative atomic mass is found in the data booklet on p7. 30. It is an average. 31. There is more 1 1H isotopes or 1 1H is more abundant. 32. 79 35Br and 81 35Br are of equal abundance or in equal proportion. 33. A covalent bond is formed by the sharing of electrons. 34. Positive nucleus + + positive nucleus Shared pair of electrons A covalent bond is formed due to the attraction of the positive nuclei of each atom for the shared pair of electrons in the overlap region. 35. Non-metals 36. Covalent discrete molecular and covalent network 4

37. (a) Any of group seven (except astatine) and hydrogen. e.g. Cl Cl or H H (b) Oxygen only: O = O (c) Nitrogen only: N N 38. Chlorine is Cl Cl and has an electron arrangement of 2,8,7 It is the third energy level which forms the covalent bonds. OR 39. Oxygen is Cl Cl and has an electron arrangement of 2,6 It is the 2 nd energy level which forms the covalent bonds. O O OR 5

40. Carbon has an electron arrangement of 2,4 and hydrogen is 1. For Carbon it is the third energy level which forms the covalent bonds. For hydrogen it is the first energy level which forms the covalent bonds. OR 41. (a) H Cl (b) linear 42. (a) O (b) Planar or bent H H 43. (a) N (c) Pyramidal H H H 44(a) H (d) Tetrahedral H C H H 6

45. (a) Low; as covalent bonds are NOT broken only weak forces between the molecules are broken. (b) No, it is a covalent molecule so does not have any free moving (delocalised) charged particles. 46. (a) High; as strong covalent bonds are broken on melting. (b) No, it is a covalent network so does not have any free moving (delocalised) charged particles. 47. Carbon dioxide (CO 2 ) is a covalent molecule with a low melting point/boiling point because only weak forces between the molecules are broken, so CO 2 exists as a gas. Whereas silicon dioxide (SiO 2 ) is a covalent network with a high melting point/boiling point because strong covalent bonds between the atoms are broken, so SiO 2 exists as a solid. 48. (a) (b) Yes, because it has delocalised electrons. 7

49.(a) (b) No, it does not have any delocalised charged particles. 50. (a) Ionic bond is the electrostatic attraction between + and ions. (b) They are formed when by the complete transfer of electron(s) from the metal to the non-metal forming + and ions. 51. A simple diagram of an ionic lattice: 8

52. (a) High (b) Not as a solid because the ions are not free to move; the ions are trapped in the crystal lattice. Conduct as a melt (liquid) or in solution (dissolved in water) because the ions are free to move. 53. (a) B (b) C (c) A 54. Discuss the following: (put only the first statement on your card, then whole answer in revision jotter) What is its physical state? (If a liquid or a gas then it must be a covalent molecule, as covalent molecules have low melting points and boiling points because only weak forces between the molecules are broken) Test the substance for electrical conductivity, as a solution and as a solid if appropriate. If the substance does not conduct in any state it is covalent. Covalent substance do not have charged particles to carry the current. If the substance conducts in solution (but not as a solid) it is ionic. Ionic substance are made up of ions which are free to move in solution but not as a solid. The free moving ions in solution can conduct electricity. 55.(a) No (b) The melting points do not compare ionic bonds with covalent bonds because when a covalent molecule melts it is the weak forces between the bonds which break NOT covalent bonds. 56. (a) Shows the ratio of atoms in the compound. (b) Shows the ratio of ions in the compound. 9

57 (a) NH 4 NO 3 (b) CuCl (c) Al(OH) 3 (d) Fe 2 (SO 4 ) 3 (e) NaHCO 3 58. (a) (Ca 2+ ) 3 (PO 4 3- ) 2 (b) (NH 4 + ) 2 S 2- (c) Ba 2+ (OH - ) 2 (d) (Fe 3+ ) 2 (SO 4 2- ) 3 (e) Mg 2+ (HSO 4 - ) 2 59.(a) Mole = formula mass expressed in grams. (b) m n GFM 60. (a) GFm of CaCl 2 = 40 + (2 x35.5) = 111g m = n x GFm = 2.5 x 111 = 277.5g (b) GFm of Na 2 SO 4 = (2x23) + 32 + (4 x 16) = 142g m = n x GFm = 1.5 x 142 = 213g (c) GFm of Mg 3 (PO 4 ) 2 = (24.5 x 3) + (31 x 2) + (16 x 8) = 263.5g m = n x GFm = 5 x 263.5 = 1317.5g 61. (a) GFm of NaNO 3 = 23 + 14 + (16 x 3) = 85g n = m / GFm = 32 / 85 = 0.38 moles (b) GFm of SiO 2 = 28 + (16 x 2) = 60g n = m / GFm = 100 / 28 = 3.6 moles (c) GFm of Ca(OH) 2 = 40 + (16 x 2) + (1x2) =74g n = m / GFm = 250 / 74 = 3.4 moles 10

62. (a) C 5 H 12 + 8O 2 5CO 2 + 6H 2 O (b) 2P + 3Cl 2 2PCl 3 (c) N 2 + 3H 2 2NH 3 (d) C 2 H 5 OH + 3O 2 2CO 2 + 3H 2 O 63. Mole statement: 1 mole C 2 H 6 2 moles CO 2 Change to mass: 30g 88g 60g X Proportion sum: 60 x 88 = 30 x X X = 60 x 88 / 30 = 176g 64. Balanced equation: S + O 2 SO 2 Mole statement: 1 mole S 1 mole SO 2 Change to mass: 32g 64g 32kg 25kg 64kg X Proportion sum: 25 x 64 = 32 x X X = 25. x 64 / 32 = 50kg 11

65. (a)(i) ph less than 7 (ii) ph greater than 7 (iii) ph = 7 (b) (i) red (ph= 1,2) to orange (ph = 3,4) to yellow (ph = 5,6) (ii) blue/green (ph= 8,9) to purple (ph = 10-14) (iii) green = ph =7 66. (a) Put the ph paper into sample and then compare colour to ph chart to get accurate PH. (b) Same as (a) only you would wet the ph paper first. 67. Sodium ethanoate has a lower ph than sodium hydroxide i.e. it is not as alkaline. (or sodium hydroxide is a stronger alkali than sodium ethanoate.) 68. Hydrochloric acid has a lower ph than ethanoic acid i.e. hydrochloric acid is more acidic. (or hydrochloric acid is a stronger acid) 69. Copper oxide is insoluble in water; the solution turned green because it was the ph of the water which was measured not copper oxide. 70. (a) A base is a substance which reacts with an acid. (b) metal oxide; metal hydroxide and metal carbonate 71(a) Acids: hydrochloric (HCl); Nitric (HNO 3 ); Sulphuric (H 2 SO 4 ) (b) Alkalis: Ammonium hydroxide (NH 4 OH); Potasium hydroxide (KOH) Sodium hydroxide (NaOH) 72. (a) Salt and water (b) neutralisation 73. (a) sodium chloride (b) ammonium sulphate (c) potassium nitrate 74. (a) Calcium nitrate + water (b) Calcium nitrate + water (c) Calcium nitrate + water + carbon dioxide 12

75.(a) CuO + 2HNO 3 Cu(NO 3 ) 2 + H 2 O (b) 2NaOH + H 2 SO 4 Na 2 SO 4 + 2H 2 O 76 (a) hydrogen (H + ) and hydroxide (OH -) ) (b) H 2 O(l) H + (aq) + OH - (aq) 77. ph is a measure of the hydrogen ion, H + (aq) concentration. 78.(a) A neutral solution has a ph = 7 because [H + ] = [OH - ] i.e. the hydrogen ion concentration = hydroxide ion concentration. (b) An acid solution has a ph less than 7 because [H + ] [OH - ] i.e. the hydrogen ion concentration is greater than the hydroxide ion concentration. (c) An alkali solution has a ph greater than 7 because [H + ] [OH - ] i.e. the hydrogen ion concentration is less than the hydroxide ion concentration 79. When acid is diluted the ph increases towards ph 7. This is because the hydrogen ion concentration is decreasing. 80. When an alkali is diluted the ph decreases toward ph 7 This is because the hydroxide ion concentration is decreasing. 13

81. Soluble metal oxides form alkaline solutions because hydroxide ions are produced which means [OH - ] [H + ] giving a ph greater than 7. 82. Soluble non-metal oxides produce acidic solutions because H + ions are produced which means [H + ] [OH - ] giving a ph less than 7. 83. (a) A spectator ion does not take part in the reaction. (b) The spectator ion in a neutralisation reaction are the salt ions, so in this example NaCl(aq) which contain the Na + and the Cl - ion. 84. H + (aq) + OH - (aq) H 2 O(l) 85. 2H + (aq) + O 2- (s) H 2 O(l) 86. 2H + (aq) + CO 3 2- (s) H 2 O(l) + CO 2 (g) 87. The spectator ions in a precipitation reaction is the soluble salt in the products, in this example, KNO 3 (aq) i.e. potassium ion, K + and the nitrate ion, NO 3 - (aq). 88. The spectator ions in a precipitation reaction is the soluble salt in the products, in this example, Ca(NO 3 ) 2 (aq) i.e. calcium ion, Ca 2+ and the nitrate ion, NO 3 - (aq). 89. (a) Titration is the technique used to find out by experiment the concentration of an acid or an alkali. (b) The end point is a colour change which indicates the end of the reaction. 14

90.(a) n = 3.5 moles v =? c = 2 moll -1 Use triangle: v n c v = n / c = 3.5 / 2 = 1.75 litres (b) n = 1.25 moles v =? c = 0.01 moll -1 Use triangle: v n c v = n / c = 1.25 / 0.01 = 125 litres 91. (a) n =? c = 2 moll -1 v = 100cm 3 = 0.1 litres Use triangle: v n c n = v x c = 0.1 x 2 = 0.2 moles (b) n =? c = 0.1 moll -1 v = 250cm 3 = 0.25 litres Use triangle: v n c n = v x c = 0.25 x 0.1 = 0.025 moles 15

92. (a) Work out moles first using n = v x c n = v x c = 1 x 0.05 = 0.05 moles Work out mass using m = n x GFM; GFM of NaOH = 23+16+1 = 40g m = 0.05 x 40 = 2g. (b) Work out moles first using n = v x c n = v x c = 0.1 x 0.1 = 0.01 moles Work out mass using m = n x GFM; GFM of KCl = 39+ 35.5 = 74.5g m = 0.01 x 74.5 = 0.745g. 93. NaOH: v = 50cm 3 = 0.05 litres; c = 0.2 mol l -1 H 2 SO 4 : v =?; c = 2 mol -1 Moles of NaOH = 0.05 x 0.2 = 0.01 moles From balanced equation, NaOH:H 2 SO 4 = 2:1 So moles of H 2 SO 4 = 0.01 /2 = 0.005 moles Use n = v x c triangle to calculate volume: V = n / c = 0.005 / 2 = 0.0025 litres 16

94. KOH: v = 10cm 3 = 0.01 litres; c = 0.1 mol l -1 HNO 3 : v = 25cm 3 = 0.025 litres ; c =? Moles of KOH = 0.01 x 0.1 = 0.001 moles From balanced equation, KOH:HNO 3 = 1:1 So moles of HNO 3 = 0.001 Use n = v x c triangle to calculate concentration: C = n / v = 0.001 / 0.025 = 0.04 mol l -1. 95. Open Ended Question Put this on a separate piece of paper to get full answer. A metal oxide if soluble dissolves in water to produce hydroxide ions, (OH - ) which means [OH - ] becomes greater than [H + ] in solution. This gives a ph greater than 7 i.e. alkaline. However, if the metal oxide is insoluble no extra hydroxide ions are produced leaving water where [H + ] = [OH - ] which gives a neutral solution, so ph = 7. So not all metal oxides produce an alkali, they have to be soluble. A non- metal oxide if soluble dissolves in water to produce hydrogen ions, (H + ) ) which means [H + ] becomes greater than [OH - ] in solution. This gives a ph greater less 7 i.e. acidic. However, if the non-metal oxide is insoluble no extra hydrogen ions are produced leaving water where [H + ] = [OH - ] which gives a neutral solution, so ph = 7. So not all non-metal oxides produce an acid they have to be soluble. 17

96. Open Ended Question Put this on a separate piece of paper to get full answer. An ionic compound is made up of a giant crystal lattice held together by the electrostatic attraction of + ions for ions. A typical ionic compound is a solid at room temperature, has high melting points and boiling points, conducts electricity in solution and as a melt but does not conduct as a solid. So sodium chloride would be tested to see if it conducts as a melt/ solution and Not as a solid. Would also look at its physical state and see if it s a solid. 18