NJC_2022_H2_Chemistry_Prelim_P3_QP

1 NJC/H2 Chem Preliminary Examination/03/2022 [Turn over NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 3 Free Response Candidates answer on Question Paper. Additional Materials: Data Booklet 9729/03 13 September 2022 2 hours READ THE INSTRUCTIONS FIRST Write your subject class, registration number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions. Section B Answer one question. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 /18 2 /19 3 /23 Section B (*circle the question you attempt) 4 /20 5 /20 Paper 3 Total /80 This document consists of 32 printed pages.

2 NJC/H2 Chem Preliminary Examination/03/2022 Section A Answer all the questions in this section. 1 (a) Amines can be synthesised from methylbenzene, shown by the following steps. CH3 CH2Cl Compound H CH2NH2 CH2Cl H2N Step 1 Step 2Step 3 Compound J Compound K Fig. 1.1 (i) Suggest the structure for compound H. [1] (ii) Suggest reagents and conditions for steps 1, 2, 3 and 4 in Fig. 1.1. [4] (iii) Suggest why the yield for step 2 is not high. [1] The Kb values of three bases, at 25 oC, are shown in Table 1.2. Table 1.2 base Kb/mol dm−3 ammonia 1.8 x 10−5 compound K 4.5 x 10−4 compound J 7.4 x 10−10 (iv) Explain the relative magnitudes of the Kb values in Table 1.2. [2] …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. Step 4

3 NJC/H2 Chem Preliminary Examination/03/2022 [Turn over …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………