2019 NYJC Prelim P3 QP

[Turn over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9729/03 Paper 3 Free Response 19 September 2019 2 hours Candidates answer Section A on the Question Paper Candidates answer on separate paper. Additional Materials: Answer Booklet Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class 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 questions. Section B Answer one question. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. 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 4 5 This document consists of 12 printed pages.

2 H2 Chemistry 9729/03 NYJC J2/2019 PRELIM Section A Answer all the questions from this section. 1 (a) When ethanoic acid reacts with ethanol to form ethyl ethanoate and water, the following equilibrium is established. CH3CO2H(l) + CH3CH2OH(l) CH3CO2CH2CH3(l) + H2O(l) H = 3.8 kJ mol1 A student mixed 1.48 g of ethanoic acid in a conical flask with 0.92 g of ethanol and 1.80 g of water. He then carefully added 0.98 g of concentrated sulfuric acid to catalyse the reaction. The flask was sealed and placed in a thermostatic water bath set at 25 C for 5 days. After 5 days, the student added phenolphthalein indicator to the flask and titrated the entire contents of the conical flask with 0.800 mol dm 3 Ba(OH)2. The indicator turned pink when 23.30 cm3 of Ba(OH)2 had been added. (i) Calculate the amount of Ba(OH)2 that has reacted with H2SO4. [1] (ii) Write a balanced equation for the reaction of ethanoic acid with Ba(OH) 2. Using your answer in (a)(i), calculate the amount of ethanoic acid present at equilibrium. [2] (iii) Write an expression for the equilibrium constant, Kc, for this reaction and calculate the value of Kc, stating its units. [3] (iv) Suggest and explain what would happen to the position of this equilibrium and the value of Kc if the temperature is decreased. [2] (b) (i) The addition of an acid to water generates heat and this process is termed as dilution. The dilution of ethanoic acid can be represented with the equation below. CH3COOH(l) CH3COO(aq) + H+(aq) Calculate the enthalpy change of dilution of ethanoic acid given the following: Hf / kJ mol1 CH3COO(aq) 486 H+(aq) 0 CH3COOH(l) 485 [1]