2022 JPJC prelim P2 Answer

© Jurong Pioneer Junior College [Turn Over NAME CLASS 21S JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2022 CHEMISTRY 9729/02 Higher 2 Paper 2 Structured Questions 14 September 2022 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and exam index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a HB pencil for any diagrams, graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 10 2 10 3 17 4 10 5 11 6 12 7 5 Penalty (delete accordingly) Bond linkages –1 / NA Significant figures & units –1 / NA Total 75 This document consists of 20 printed pages.

2 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2022 Answer all the questions in this section. 1 (a) Figure 1.1 shows the third ionisation energies of eight consecutive elements A to H, in the Periodic Table. [Note that letters A to H are not the atomic symbols of the elements concerned.] Figure 1.1 For Examiner’s Use (i) Write an equation, including state symbols, to represent the third ionisation energy of element A. [1] A2+(g) ⟶ A3+(g) + e- (ii) From Figure 1.1, suggest the identity of B. Explain how you arrived at your answer. [2] The large decrease in 3 rd IE from F to G implies that G 2+ has 1 more quantum shell of electrons than F2+ / 3rd electron to be removed from F is from the inner quantum shell. The valence shell configuration of G2+ is ns1 and hence, the valence shell configuration of G is ns2 np1 (i.e. Al). OR This also implies that the valence shell configuration of B2+ is (n-1)s2 np2 and hence, the valence shell configuration of B is ns2 np4 . OR F is in group 2 / G is in group 13 Hence, B is oxygen. Cannot accept sulfur. (iii) Explain why the third ionisation energy of element D is slightly lower than that of element C. [1] C2+: 1s22s22p3 D2+: 1s22s22p4 The inter −electronic repulsion / repulsion between the paired 2p electrons in D 2+ makes it easier to remove a paired electron than an unpaired 2p electron of C2+ which do not experience such repulsion. Hence, the 3rd IE of D is lower than that of element C. Third Ionisation energy/ kJ mol−1

3 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2022 [Turn Over (b) Nitrogen and phosphorus are elements of Group 15 in the Pe