2024 NYJC H1 Chem 8873 P1 Answers

J2 Prelim Exam 2024 H1 Chemistry Paper 1 Answers and Comments Page 1 of 7 Nanyang JC J2 Prelim Exam 2024 H1 Chemistry 8873/01 Paper 1 MCQ Answers and Comments Qn Ans Qn Ans Qn Ans Qn Ans Qn Ans Qn Ans 1 B 6 C 11 A 16 B 21 A 26 C 2 C 7 A 12 D 17 B 22 A 27 D 3 C 8 A 13 D 18 C 23 D 28 C 4 C 9 D 14 B 19 A 24 B 29 A 5 D 10 B 15 D 20 B 25 A 30 B 1 B n(ethanol) = 2046.0 = 0.4347 mol n(propanoic acid) = 3074.0 = 0.4054 mol propanoic acid is the limiting reagent m(ethyl propanoate) = 0.4054102.0 = 41.35g yield of ester = (2241.35)100% = 53% 2 C AlxCy + H2O → gas gas + O2 → CO2 + H2O n(CO2) = 0.07224 = 0.003 mol n(C) in every mol of gas = n(C) in every mol of compound A = 0.003 mol Option A: n(Al2C3) = 0.14490.0 = 0.0016 mol n(C) in Al2C3 = 3  0.0016 = 0.00480 mol Option B: n(Al3C4) = 0.144129.0 = 0.00112 mol n(C) in Al3C4 = 4  0.00112 = 0.00447 mol Option C: n(Al4C3) = 0.144144.0 = 0.0010 mol n(C) in Al4C3 = 3  0.0010 = 0.00300 mol Option D: n(Al5C3) = 0.144171.0 = 0.000842 mol n(C) in Al5C3 = 3  0.000842 = 0.00253 mol 3 C Zn → Zn2+ + 2e− Mole ratio of Zn : VO2+ : e−  1 : 2 : 2  ½ : 1 : 1  1 mol of VO2+ gained 1 mol of e− Since ON of V in VO2+ = +5, final ON of V in Y is +4 V5+ + e− → V4+ Ion Y is VO2+ (ON of V is +4) 4 C + X → + p+ The number of subatomic particles (protons & neutrons) should be balanced. no. of protons no. of neutrons 32 15P and p+ 15 + 1 = 16 (32 – 15) + 0 = 17 32 16S 16 32 – 16 = 16 X 0 1

J2 Prelim Exam 2024 H1 Chemistry Paper 1 Answers and Comments Page 2 of 7 5 D Al: 1s2 2s2 2p6 3s2 3p1 Option A is incorrect as e lectrons are present in five different energy levels. Option B is incorrect as t here are 7 electrons in p orbitals and 6 electrons in s orbitals. Option C is incorrect as the occupied orbital of lowest energy (1s) is spherical. 6 C 1: bond angle wrt O decreases from 109o in ice (0lp, 4bp – 2 covalent bonds and 2 H- bonds: see below) to 105o in water (2bp, 2lp) 2: bond angle wrt S increases from <120o in SO2 (2bp, 1lp) to 120o in SO3 (3bp, 0lp) 3: bond angle wrt C increases from 109o in RCH(OH)R’ (4bp, 0lp) to 120o in ketone RCOR’ (3bp, 0lp) C OH H R R' 109o R C O R'120o 4: bond angle wrt Al decreases from 120o in AlCl3 (3bp, 0lp) to 109o Al2Cl6 (4bp, 0lp) 7 A CCl4 and C 6H14 are non -polar molecules that forms only id-id interactions. For A, CH2Cl2 and (CH 3)2CO are polar molecules that can form pd-pd interactions. For B and C, stronger pd -pd interactions are broken and weaker id -id interactions are formed between non-polar molecule mixed with a polar molecule hence heat is taken in. Similarly for D, strong hydrogen bonds between CH 3CH2OH molecules are broken and only weak id -id interactions are