2022 SASS A-Z Chem Prelims AnsPt2

1 A – Z School’s Preliminary Papers 4 Express Chemistry ANSWERS: Part 2 F Fuhua Secondary School G Geylang Methodist School (Secondary) H Hua Yi Secondary School I Holy Innocents’ High School J Juying Secondary School FUHUA SECONDARY SCHOOL Paper 1 Paper 2 2022 Secondary 4 Pure Chemistry (6092) Prelim Paper 1 Suggested Answers 1 2 3 4 5 6 7 8 9 10 D A A B B B B A C C 11 12 13 14 15 16 17 18 19 20 B B D B C B D A C B 21 22 23 24 25 26 27 28 29 30 A B C C B D C B B D 31 32 33 34 35 36 37 38 39 40 B A D A B A C B C C 1 FUHUA SECONDARY SCHOOL Sec 4E Chemistry 6092 Preliminary Examinations 2022 – Mark Scheme PAPER 2 Section A [50 marks] Q Answer Mark Remarks 1a Rb and F 1 bi Na and S 1 bii two ions of Na+ [1] and one ion of S2- [1] 2 e.c.f from bi c Al and Zn 1 d Meting point decreases and reactivity increases down Group I. [1] Melting point increases and reactivity decreases down Group VII. [1] 2 e Ca + 2H2O → Ca(OH)2 + H2 1 Total 8 marks 2ai 6NO + 4NH3 → 5N2 + 6H2O 1 ii Oxidation state of nitrogen increases from -3 in NH3 to 0 in N2. Hence ammonia is oxidised. [1] Oxidation state of nitrogen decreases from +2 in NO to 0 in N2. Hence NO is reduced. [1] 2 b NO will react with oxygen to form NO2, which reacts with water and oxygen to form nitric acid which dissolves in water; to form acid rain which erodes limestone buildings and corrodes metallic structures / kills aquatic life by lowering the pH of water bodies.[1] 1 1 c Any one of the following • Producing ammonia on-site is easier as minimum storage and transportation of ammonia is required. • Not producing ammonia on-site means ammonia, being a gas, must be stored in thick pressurised containers which are heavy and difficult to transport. • Do not need to burn fuels during transportation so less greenhouse gas pollution. 1 REJECT gas escapes/ recycled gases as other plants also can. time used for transportation d At high temperature, the urea and water have more kinetic energy and collide more frequently [;] More urea and water particles collide with energy greater than or equal to the activation energy [;] Leading to higher frequency of effective collisions between urea and water. [;] 3; [2] 1-2; [1] e Ammonia has a simple molecular structure [;] with weak intermolecular forces of attraction between molecules [;] hence little amount of energy taken in to overcome the forces. [;] 2 3; [2] 1-2; [1] Total 10 marks 3a 1000 1 b Add aqueous bromine to samples of each polymer separately.[1] If reddish-brown aqueous bromine decolourises rapidly, sample is A. If aqueous bromine remains reddish-brown, then sample is C. [1] 2 c False, True, True, False 2 4  : [2] 2-3  : [1] d 2 Must show all bonds SASChemistry 2022edition

2 1 FUHUA SECONDARY SCHOOL Sec 4E Chemistry 6092 Preliminary Examinations 2022 – Mark Scheme PAPER 2 Section A [50 marks] Q Answer Mark Remarks 1a Rb an