2022 TJC Prelims H2 Paper 1 MCQ Ans Only

2 9729 / TJC Prelims / 2022 TJC 2022 H2 Chemistry Paper 1 Answer Key 1 2 3 4 5 6 7 8 9 10 D C A B D B B C A A 11 12 13 14 15 16 17 18 19 20 D C B D B A C A B D 21 22 23 24 25 26 27 28 29 30 C B D C A D C B C A 1 Answer: D Worked Solution: Number of neutrons in 31P3– = 31 – 15 = 16 Number of neutrons in 32S2– = 32 – 16 = 16 Thus, 31P3– are 32S2– are isotonic. Angle of deflection of species in electric field  𝑐ℎ𝑎𝑟𝑔𝑒 𝑚𝑎𝑠𝑠 31P3– has a higher charge and a smaller mass than 32S2–. The angle of deflection of 31P3– will be greater than that for 32S2–. 2 Answer: C Worked Solution: 3rd electron of B comes from an inner shell, B has 3 valence electron and is from Group 13. C is from Group 15. 3 Answer: A Worked Solution: Ga Ge As Se Br Kr Rb Sr 200 400 600 800 1000 1200 1400 30 31 32 33 34 35 36 37 38 39 First Ionisation Energy Atomic Number

3 9729 / TJC Prelims / 2022 1: correct, from diagram, IE of Ga < Ge < As 2: wrong, Se < As < Br 3: correct, Se < Br < Kr 4: wrong, Sb < As < P 4 Answer: B Worked Solution:  A O is the most electronegative element in Group 16. Thus, the C=O bond is the most polar amongst the three bonds. ✓ B O is the most electronegative element in Group 16. Since C= Z bond is less polar than C=Y bond, this suggests that Y is more electronegative than Z. (See diagrams above.)  C While this statement is true, it does not explain the observed trend.  D Bond length has little bearing on net molecular dipole. 5 Answer: D Worked Solution: SO2 has bent shape, bond angle < 120o. SO3 has trigonal planar shape, bond angle is 120o. 6 Answer: B Worked Solution: PV= nRT A. Incorrect. The number of moles of L is greater than number of moles of M B. Correct. At constant T, PV= n x constant C. Incorrect. At constant T, V = nRT/P, straight line pass through origin, different gradient for L & M D. Incorrect. At constant P, V = (nR)/p x T = constant x T net molecular dipole = 0 equal bond polarity C OO C YO net molecular dipole = 0.71 C=O bond is more polar than C= Y bond, which results in net molecular polarity. C ZO net molecular dipole = 0.73 C=O bond is more polar than C= Z bond, which results in net molecular polarity. However, C= Z bond is less polar than C= Y bond, which results in a larger net molecular dipole.

4 9729 / TJC Prelims / 2022 7 Answer: B Worked Solution: element pH of solution when oxide of element is added to water pH of solution when chloride of element is added to water X Na Na2O + H2O → 2NaOH pH = 13 NaCl(aq), pH = 7 Y P P4O10 + 6H2O → 4H3PO4 pH = 2 PCl5 + 4H2O → H3PO4 + 5HCl pH = 2 Z Al Al2O3 is insoluble in water pH = 7 AlCl3 undergoes hydration and hydrolysis. pH of solution is about 3. 8 Answer: C Worked Solution: Ionic radii of group 2 cations increases down the group. Charge density and polarising power decrease down the group, thermal stability increases down the group. 9 Answer: A