CJC H2 Chem 2012 Prelim P1 QP

CATHOLIC JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS Higher 2 CHEMISTRY 9647/01 Paper 1 Multiple Choice Wednesday 29 August 2012 Additional Materials: Multiple Choice Answer Sheet 1 hour Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid. Write and/or shade your name, NRIC / FIN number and HT group on the Multiple Choice Answer Sheet in the spaces provided. There are forty questions in this paper. Answer all questions. 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. Read the instructions on the Multiple Choice Answer Sheet very carefully. 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. Calculators may be used. This document consists of 18 printed pages and 0 blank page.

2 9647/01/CJC JC2 Preliminary Exam 2012 Section A For each question there are four possible answers, A , B , C and D. Choose the one you consider to be correct. 1 Gallium ( Ar = 69.7) occurs naturally as two isotopes, 69 31 Ga and 71 31 Ga. What is the percentage of 71 31 Ga atoms in a sample of naturally occurring gallium? A 33 % B 35 % C 60 % D 65 % 2 The mineral tellurite, TeO2 (Mr = 160.0) is often used in the manufacture of optic fibres. It was found that 1.01 g of TeO 2 in an ore sample required exactly 60 cm 3 of 0.035 mol dm –3 acidified K 2Cr2O7 for complete reaction. In this reaction, Cr 2O72– is converted into Cr3+. What is the oxidation state of Te in the final product? A +2 B +3 C +5 D +6 3 Use of the Data Booklet is relevant to this question. What do the ions 35Cl– and 40Ca2+ have in common? A Both ions have 18 neutrons. B Both ions have more protons than neutrons. C Both ions contain the same number of nucleons. D Both ions have an outer electronic configuration 3s2 3p6. 4 Carbodiimides are often used in organic synthesis as dehydrating agent to activate carboxylic acids towards amide or ester formation. Carbodiimides consist of the general structure, RN=C=NR where R is an alkyl group. What is the most likely bond angle at each nitrogen atom in carbodiimides? A 107° B 118° C 120° D 180° 5 Myoglobin, Mb, is an oxygen-carrier protein that exists in the muscle fibres of most mammals. Each Mb molecule will bind to one O 2 molecule, according to the following equation. Mb(aq) + O2(aq) MbO2(aq) Kc = 1×106 mol–1 dm3 Given that the concentration of O 2 is 6.5 × 10 –6 mol dm –3, what is the percentage of MbO2 in a Mb-MbO2 mixture? A 50.5 % B 65.0 % C 86.7 % D 88.4 %

3 9647/01/CJC JC2 Preliminary Exam 2012 [Turn over 6 The enthalpy changes involving some oxides of nitrogen are given below: N2(g) + O2(g) → 2NO(g) ∆H = +180 kJ mol–1 2NO2(g) + 1 2O2(g) → N2O5(g) ∆H = –55 kJ