2024 Prelims TJC H2 Chem P1 (Ans)

1 9729 / TJC PRELIM / 2024 TEMASEK JUNIOR COLLEGE 2024 JC2 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9729/01 Paper 1 Multiple Choice 12 September 2024 1 hour Additional Materials: Multiple Choice Answer Sheet (OMS) Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. There are thirty questions In this paper. Answer all questions. For each question there are four possible answers A, B, C, D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer sheet. Read the instructions on the Answer sheet very carefully. Write your name & Civics Group on the Answer sheet. Shade your index number in the appropriate boxes. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. This document consists of 14 printed pages and 2 blank pages. Write your name and Civics Group Index number (refer to entry proof)

2 9729 / TJC PRELIM / 2024 For each question there are four possible answers, A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet (OMS). 1 Use of the Data Booklet is relevant to this question. Chlorine radicals is one of the main chemical species responsible for the depletion of ozone from the stratosphere. What does 35Cl contain? protons neutrons electrons A 18 35 17 B 18 35 18 C 17 18 17 D 17 18 18 Answer: C Chlorine radical is a chlorine atom. The proton number = electron number = 17. The neutron number = nucleon number – proton number = 35 – 17 = 18 2 Which compound is composed of cation and anion that has the same number of electrons as each other? 1 K2O2 2 NaN3 3 NH4F 4 K2CO3 A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4 Answer: A Cation Number of e- Anion Number of e- 1 K+ 19 – 1 = 18 O22- (2 x 8) + 2 = 18 2 Na+ 11 – 1 = 10 N3- 3(7) + 1 = 22 3 NH4+ 7 + 4 – 1 = 10 F- 9 + 1 = 10 4 K+ 19 - 1 = 18 CO32- 6 + 3(8) + 2 = 32

3 9729 / TJC PRELIM / 2024 [Turn over 3 Use of the Data Booklet is relevant to this question. The sixth ionisation energies of four different elements are shown below. The elements are arsenic, selenium, antimony and tellurium (though not necessarily in that order) from Groups 15 and 16. Which of the following shows the sixth ionisation energy of antimony? A 12300 B 10400 C 7880 D 6820 Answer: B Arsenic (As) and Antimony (Sb) are in Group 15 and have 5 valence electrons in their valence shell. The sixth ionisation energies of As and Sb involve the removal of electron from an inner electron shell, hence the values are large → options A and B. Sb is in a Period below As, the electron to be removed from Sb is further