RI 2021 A-Level H2 Chem Solution

This document is copyrighted, please do not reproduce it without permission © Raffles Institution 2021 A-Level H2 Chemistry Paper 1 Suggested Solutions 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 B D C B C D B D D A C A B B A 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 A C B D C A A A B B D B C C D Q1(B) 1 Correct. Angle of deflection is proportional to q m . Since m electron < m proton, electrons have a greater angle of deflection and are deflected to a larger extent than protons. 2 Correct. Electrons are attracted to the positive plate while protons are attracted to the negative plate i.e. the electron beam are deflected in the opposite direction to the proton beam. 3 Incorrect. The proton beans will travel in a curve path towards the negative plate. Q2(D) Q in the ionic nitrate, QNO3, exists as Q+. Since Q+ has 80 electrons, Q has 81 electrons and 81 protons. From the Periodic table, Q is the element thallium which belongs to group 13. The nucleon number of Q is 81 + 122 = 203. Q3(C) A Incorrect. 2nd IE of F : F+ → F2+ + e– [He]2s22p4 [He]2s22p3 3rd IE of Al : Al2+→ Al3++ e– [Ne]3s1 [Ne] 2nd IE of F is greater because the electrons are removed from an inner electronic shell. B Incorrect 3rd IE of electron removed from F 2p Ne 2p Na 2p Mg 2p Al 3s C Correct. 4th IE of Na : Na3+ → Na4+ + e– [He]2s22p4 [He]2s22p3 3rd IE of Ne : Ne2+→ Ne3+ + e– [He]2s22p4 [He]2s22p3 Na3+ and Ne 2+ have the same electronic configuration and experience the same shielding effect. 4 th IE of Na is greater due to the greater nuclear charge of Na which causes the 2p electrons of Na3+ to experience a greater attraction to the nucleus, requiring more energy to remove. D Incorrect. Successive IE’s always increase even if the electrons are removed from different shells. This is because the nuclear charge remains the same, but the number of electrons and shielding effect experienced by the remaining electrons decreases. Hence the electrostatic attraction between the nucleus and the outermost electron increases, resulting in an increase in energy required to remove each subsequent electron. Q4(B) Since there is a large jump between the 7 th and 8th IE for element W, the 8 th electron is removed from an inner shell i.e. W has 7 valence electrons and is from group 17. Since W, X, Y and Z are consecutive elements, X is from group 18, while elements Y and Z are from groups 1 and 2 of the next period respectively. X, the group 18 element, has a higher first IE than W, the group 17 element of the same period since IE increases across the period. X also has the higher first IE then Y and Z since Y and Z are from the next period and their valence electrons are further away from the nucleus and experience grea