2023_NJC_H2_Chemistry_Prelim_Paper_3_QP

1 NJC SH2 Preliminary Examination 9729/03/23 [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 14 September 2023 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 /20 2 /16 3 /24 Section B 4 /20 5 /20 Paper 3 Total /80 This document consists of 32 printed pages.

2 NJC SH2 Preliminary Examination 9729/03/23 Section A Answer all the questions in this section. 1 (a) Table 1.1 list physical properties of some Period 4 elements. Table 1.1 property K Ca Fe As Se relative atomic mass 39.1 40.1 55.8 74.9 79.0 atomic radius (metallic) / nm 0.197 0.126 melting point / K 1112 1808 density / g cm−3 1.54 7.86 1st I.E. / kJ mol−1 944 941 2nd I.E. / kJ mol−1 3070 1150 (i) Explain why the atomic radius of Fe is less than that of Ca. [2] (ii) Use relevant data from Table 1.1 to explain why the density of Fe is significantly greater than that of Ca. (no calculations are required) [2] (iii) Suggest why the melting point of Fe is significantly higher than the melting point of Ca. [2] (iv) With reference to the electronic configuration of K and Ca, explain why the 2nd I.E. of Ca is lower than that of K. [2] (v) With reference to the electronic configurations of As and Se, explain why the 1st I.E. of Se is lower than that of As. [2] …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. ……………………………………………………………………………………………..

3 NJC SH2 Preliminary Examination