SAJC_H2_CHEM_P2_Ans Prelim

1 [Turn Over Name: Class: ST ANDREW’S JUNIOR COLLEGE JC 2 Preliminary Exam (TUTOR’S COPY) Chemistry Higher 2 9647/02 31 August 2016 Paper 2 2 hours Candidates answer in the spaces provided on the question paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use: Question Marks 1 2 3 4 5 6 7 Total (72 marks) This document consists of 27 printed pages (including this page) and 1 blank page.

2 [Turn Over 1 A student found a bottle of solid benzoic acid in the school laboratory. She was tasked to determine the standard enthalpy change of neutralisation of benzoic acid. The standard enthalpy change of neutralisation is when one mole of water is formed between an acid and a base. H+ (aq) + OH− (aq)  H2O (l) You may assume you are provided with the following:  FA 1, aqueous sodium hydroxide, NaOH  Solid benzoic acid  Polystyrene (styrofoam) cups  Apparatus normally found in a school laboratory Before carrying out the experiment, an aqueous solution of 2.00 mol dm -3 benzoic acid (FA 2) is first prepared. Subsequently, in separate experiments, different volumes of FA 2 and FA 1 are mixed while keeping the total volume of the reaction mixture constant. In each experiment, the temperature rise, ∆T, is to be determin ed. A graph of ∆T against volume of FA 1 used is then plotted. Data from the graph can then be used to determine:  the ∆Tmax,  the concentration of FA 1,  the enthalpy change of neutralisation between FA 1 and FA 2. It is given that 4.18 J is required to raise the temperature of 1 cm 3 of any solution by 1 oC. (a) Write an equation to represent the standard enthalpy change of neutralisation between sodium hydroxide and benzoic acid. [1] C6H5COOH(aq) + NaOH(aq) → C6H5COO-Na+(aq) + H2O(l) (b) (i) Write a detailed plan to prepare 2.00 mol dm-3 solution of FA 2. [3] To prepare 250.0 cm3 of 2.00 mol dm–3 benzoic acid (FA 2) Molar mass of C7H6O2= 122 g mol–1

3 [Turn Over 1) Amount present in 250.0 cm3 of 2.00 mol dm–3 solution = 61.0 g 2) Use a weighing balance to measure accurately 61.0 g (minimum 61.0 g or maximum 62.0 g) of solid C 7H6O2 in a cl