SRJC H2 CHEM P2

SRJC 2009 9746/02/PRELIM/2009 [Turn Over SERANGOON JUNIOR COLLEGE General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CLAS S INDEX NUMBER CHEMISTRY 9746/02 Preliminary Examination 26 August 2009 Paper 2 Structured 1 hr 30min Additional Materials: Data Booklet Writing Papers Candidates answer on the Question Paper. READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. You may use a soft pencil for any diagrams, graphs or rough work. Answer all questions in the space provided. At the end of the examination, fasten all your work securely together. The number of marks is given in the brackets [ ] at the end of each question or part questions. For Examiner’s Use 1 2 3 4 5 Total This document consists of 12 printed pages and 0 blank page

For 2 Examiner’s Use SRJC 2009 9746/02/PRELIM/2009 [Turn Over 1 The atomic and cationic radii of Period 3 elements, Na to C l, are plotted in the graph below, in order of increasing atomic number. Na Mg Al Si P S ClNa+ Mg2+ Al3+ Si4+ 0.00 10 11 12 13 14 15 16 17 18 Radius / nm Proton no. Atomic & Ionic Radii vs. Proton no. for Elements in Period 3 P3- S2- Cl- 0. 05 0.10 0.15 0.20 0.25 Atomic Radii Cationic Radii Anionic Radii (a) Explain each of the following: (i) The atomic radius decreases across the period from Na to Cl. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… (ii) The cationic radius of Na+ is smaller than its atomic radius. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [4]

3 For Examiner’s Use (b) (i) Indicate, on the graph, the relative positions of the ions, P3–, S2– and Cl–. (ii) Explain your answer in (b)(i). ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [3] (c) (i) Write down the electronic configuration of sulphur in its ground state. ………………………………………………………………………………… (ii) Explain the following phenomenon: Sulphur can react with fluorine to form SF2, SF4 and SF6 but oxygen can react with fluorine to form OF 2 only. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] (d) The successive ionisation energies in kJ mol –1 of an element A are as follows: 740, 1500, 7700, 10500, 13600, 18000, 21700 State the Group in which A belongs to and explain your answer. Suggest the formula of the chloride of A. ……………..………………………………………………………………………… ……………………..………………………………………………………………… ……………………………...……………………………………………………….. ……………………………………………………………………………………….. [3] [Total: 12] SRJC 2009 9746/02/PRELIM/2009 [Turn Over

4 For Examiner’s Use 2 A pheromone is a chemical s ubstance that, when secreted by an individual of a species, for example the insects, can elic it a certain type of behaviour in other individuals. Compound B below is an alarm pheromone secreted by several species of ants, to send out warning signals to other ants. CH3CH2CH2CH=CHCHO Compound B (a) State the type of isomerism that exists in compound B. ……………………………………………………………………………………………[1] (b) Compound B can undergo the following conversion: CH3CH2CH2CH CHCHO Reaction I CHCCH3CH2CH2CH OH CN H Compound B Compound C State the reagents and condition required for reaction I . Outline the mechanism of reaction I, including curly arrows, showing the movement of electrons, and all charges. Reagents and Condition: …………………………………………………………. [4] SRJC 2009 9746/02/PRELIM/2009 [Turn Over

5 For Examiner’s Use (c) (i) Compound C has a chiral carbon. Illustrate the isomerism exhibited with the aid of structural formulae. (ii) Compound C, however, does not rotate plane polarised light. Explain this phenomenon with reference to the mechanism mentioned in (b). ……………………………………………………………………………….. ….……………………………………………………………………………. .………………………………………………………………………………. ……………………………………………………………………………….. [3] (d) The reaction of hydroxide ion with chloromethane to yield methanol and chloride ion is an example of nucleophilic substitution reaction: OH─ + CH3Cl  CH3OH +Cl─ The value of ∆H for the reaction is –75 kJ mol –1, and the value of ∆ S is +54 J mol–1. (i) What is the value of ∆G at 298 K? ∆G  =……………..kJ mol –1 (ii) Predict whether the reaction is feasible at 298 K? ……………………………………………………………………………… (iii) Will temperature affect the feasibility of the reaction? Explain. ……………………………………………………………………………….. [4] [Total: 12] SRJC 2009 9746/02/PRELIM/2009 [Turn Over

6 For Examiner’s Use 3 Ammonia is manufactured in the Haber process. N2 (g) + 3H2 (g) 2NH 3 (g) ∆H = -92 kJ mol-1 Le Chatelier’s principle predicts that the highest yield of ammonia is obtained at high pressure and low temperature. Ho wever, in practice, these conditions are not used. (a) Using Le Chatelier’s principle, explain why the above conditions are used. ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………. ……………………………………………………………………………………… [3] (b) Suggest two reasons why these conditions of high pressure and low temperature are not used in the industry. ……………………………………………………………………………………… ……………………………………………………………………………………… [1] (c) The gases are usually passed through a tower packed with lumps of metal. Identify the metal used and suggest a reason for the use of this metal. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [2] SRJC 2009 9746/02/PRELIM/2009 [Turn Over

7 For