JPJC 2023 Prelim P2 QP

© Jurong Pioneer Junior College [Turn Over NAME CLASS 22S JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2023 CHEMISTRY 9729/02 Paper 2 Structured Questions September 2023 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and index number in the spaces at the top of this page. Write in dark blue or black pen. You may use a HB pencil for any diagrams or 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. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 13 2 10 3 10 4 13 5 16 6 13 Penalty (delete accordingly) Lack 3sf in final answer –1 / NA Missing/wrong units in final ans –1 / NA Bond linkages –1 / NA Total 75 This document consists of 19 printed pages and 1 blank page.

2 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2023 Answer ALL the questions in the spaces provided. 1 (a) Halogens can react with alkanes to form halogenoalkanes. The boiling points of a few halogenoalkanes, in Kelvin, are given in Table 1.1. Table 1.1 compound boiling point / K CH3F 195 CH3Cl 249 CH3CH2F 236 For Examiner’s Use (i) Comment on the relative bond polarity of C −F bond in CH3F and C−Cl bond in CH3Cl. ……………………………………………………………………………………. ……………………………………………………………………………………. [1] (ii) Explain the difference in boiling point between CH3F and CH3Cl. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. [1] (iii) Both CH3Cl and CH3CH2F are isoelectronic. Explain the difference in boiling point between CH3Cl and CH3CH2F. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. [1]

3 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2023 [Turn Over (b) Halogens can react to form interhalogen compounds such as F3. Consider a molecule of F3, the central atom is surrounded by five pairs of electrons in a trigonal bipyramidal arrangement. There are three electron pairs arranged on the same plane in equatorial positions and two electron pairs arranged perpendicular to the plane in axial positions. Three possible different molecular arrangements of F3 are shown in Table 1.2. For Examiner’s Use Table 1.2 Lone pairs in axial positions. Lone pairs in equatorial positions. Lone pairs in axial and equatorial positions. number of lone pairs at 90 relative to one another 0 0 1 number of bond pair and lone pair at 90 relative to one another 3 relative s