NJC 2021 A Level Chem Solution

H2 Chemistry TYS 2021 suggested answers Paper 1 Answer Key 1 B 11 C 21 A 2 D 12 A 22 A 3 C 13 B 23 A 4 B 14 B 24 B 5 C 15 A 25 B 6 D 16 A 26 D 7 B 17 C 27 B 8 D 18 B 28 C 9 D 19 D 29 C 10 A 20 C 30 D 2021 A level Paper 1 suggested worked solutions 1 Ans: B Statement 1: Correct, as electrons are lighter than protons and angle of deflection ∝charge mass Statement 2: Correct, as electron and proton are attracted towards oppositely charged plate due to electrostatic forces of attraction. Statement 3: Incorrect, as the beam do not travel in a straight line but curved path. 2 Ans: D Since the formula of compound is QNO3, cation is Q+. Hence since there is 80 electrons, there should be 81 protons in element Q.  Element is Tl in group 13. As such, nucleon number = 81 + 122= 203. 3 Ans: C Statement A: Incorrect F+: 1s2 2s2 2p4 Al2+: 1s2 2s2 2p6 3s1 Electron is removed from second electronic shell of F which is much closer to the nucleus (vs from 3rd electronic shell for Al) hence more energy is required to overcome the stronger attraction between the nucleus and valence electron. Statement B: Incorrect, 3rd I.E. is removing electron from gaseous X2+ to form X3+ F2+: 1s2 2s2 2p3 Ne2+: 1s2 2s2 2p4 Na2+: 1s2 2s2 2p5 Mg2+: 1s2 2s2 2p6 Al2+: 1s2 2s2 2p6 3s1 Al 3rd IE involve electron removed from electronic shell 3 while the rest are removed from electronic shell 2. Statement C: Correct, Na3+ and Ne2+ are isoelectronic (1s2 2s2 2p4 ) with same shielding effect. Na3+ has a greater proton number, hence a greater nuclear charge and stronger nuclear attraction for the most loosely held electron, resulting in a greater ionisation energy value. Statement D: Incorrect, successive I.E. involves removal of electrons from the outer filled electronic shell towards the inner filled electronic shell, and hence are not all taken from the same shell.

2021 A level Paper 1 suggested worked solutions 4 Ans: B For element W, there is a big jump in IE between 7th and 8th IE, implying 8th electron is in inner electronic shell and hence 7 valence electrons, thus W is a group 17 element. Since the elements are consecutive, it means X is in group 18 of the same period, n. Y and Z are in group 1 and group 2 of the next period (n+1). As 1st IE generally increases across a period and decreases down the group, X has the highest 1st I.E. E.g. W is F, X is Ne, Y is Na, Z is Mg, Ne has the highest first I.E. 5 Ans: C From C2H6 to C2H4 to C2H2, Bond order of the C-C changes from 1 (C−C) to 2 (C=C) to 3 (C≡C).  Bond energy increases  Bond length decreases. 6 Ans: D molecule Molecular shape Polarity A BCl3 Trigonal planar Non-polar B NCl3 Trigonal pyramidal Polar C SO2 Bent polar D CHCl3 tetrahedral polar 7 Ans: B Predominant IMF Average number of H bond per molecule M H-bond 2 N Pd-pd NA P H-bond 1 Q H-bond 1 Between P an