JJC 2015_H1_CHEM_P2_Ans Prelims

[Turn over JURONG JUNIOR COLLEGE 2015 JC 2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME Suggested Answers CLASS 15S CHEMISTRY 8872/02 Paper 2 Structured Questions 28 August 2015 2 hours Candidates answer Section A on the Question Paper. Additional Materials: Answer Paper Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and exam index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all the questions. Section B Answer two questions on separate answer paper. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 2 3 4 B5 B6 B7 Total This document consists of 14 printed pages and no blank page.

2 © Jurong Junior College 8872/02/ J2 PRELIMINARY EXAMINATION/2015 [Turn over Section A Answer all the questions. 1 Ethanoic acid, also known as acetic acid, is a colourless liquid that has a strong and distinct pungent and sour smell. Aside fr om culinary uses, as flavouring and as a preservative, ethanoic acid is used to make many polymers and fibres. It can be made by the following method: For Examiner’s Use (a) Draw the structure of compound A. [1] (b) (i) Ethanoic acid can be formed from the oxidation of ethanol. Suggest suitable reagent and conditions to perform this reaction. acidified KMnO4/ K2Cr2O7, heat (ii) Write a balanced equation to represent the reaction in (b)(i). CH3CH2OH + 2[O]  CH3CO2H + H2O [3] (c) 2-chloroethanoic acid can be formed from ethanoic acid using suitable reagents and conditions via substitution reaction. Explain why 2-chloroethanoic acid and ethanoic acid has different acidity. 2-chloroethanoic acid is a stronger acid Cl is an electron withdrawing atom which disperses the negative charge on the O− and stabilises the ClCH2CO2 − ion. [2]

3 © Jurong Junior College 8872/02/ J2 PRELIMINARY EXAMINATION/2015 [Turn over 1 (d) A gas is said to exhibit ideal gas behavior if it obeys the ideal gas equation pV = nRT where p = pressure of gas in Pa, V = volume of gas in m3, n = amount of gas (mol), R = 8.31 J K−1 mol−1 (a constant), and T = temperature in K. For Examiner’s Use Three experiments were performed where different masses of ethanoic acid were expanded into a vessel of volume 0.0150 m 3 at different pressures and at a temperature of 100 oC. Experiment Mass of ethanoic acid/ g Pressure/ Pa Relative molecular mass 1 0.002 6.346 65.1 2 0.015 31.011 100 3 0.050 86.128 120 Accept exact answer 100.0, 120.0