MJC_H2_CHEM_P2_answers Prelim

Name: _______________________ Class: 13S_________ Reg Number: ______ MERIDIAN JUNIOR COLLEGE Preliminary Examination Higher 2 _______________________________________________________________________________ Chemistry 9647/02 Paper 2 Structured Questions 19 September 2014 2 hours Additional Materials: Data Booklet _______________________________________________________________________________ INSTRUCTIONS TO CANDIDATES Write your name, class and register number in the spaces provided at the top of this page. Write your calculator brand and model/number in the box provided above. Answer all questions in the spaces provided on the question paper. All working must be shown clearly. INFORMATION FOR CANDIDATES This document consists of 20 printed pages. Examiner’s Use Paper 1 MCQ / 40 Paper 2 Q1 / 12 Q2 / 12 Q3 / 11 Q4 / 13 Q5 / 14 Q6 / 10 Paper 3 / 80 Total / 192 Percentage Grade The number of marks is given in brackets [ ] at the end of each question or part question. You are reminded of the need for good English and clear presentation in your answers. Calculator Model / No.

2 [Turn over 1 Planning (P) The enthalpy change of neutralisation is the enthalpy change when one mole of water is formed in the reaction between an acid and a base. H+(aq) + OH−(aq)  H2O(l) You are required to determine the enthalpy change of neutralisation between a strong base and a carboxylic acid through a series of experiments. You may assume you are provided with the following:  FA 1, aqueous sodium hydroxide, NaOH  FA 2, 1.50 mol dm–3 propanoic acid, CH3CH2COOH  polystyrene (styrofoam) cups  apparatus normally found in a school laboratory. In separate experiments, different volumes of FA 1 and FA 2 are mixed while keeping the total volume of the reaction mixture constant. In each exper iment, the temperature rise, ∆T , is to be determined. When a graph of ∆T against volume of FA 1 used is plotted, it is observed that the t emperature rise will increase, and then decrease when different volumes of FA 1 are used. Data from the graph can then be used to determine:  the concentration of sodium hydroxide, NaOH, in FA 1.  the enthalpy change of neutralisation between NaOH and CH3CH2COOH. It is given that 4.18 J is required to raise the temperature of 1 cm 3 of any solution by 1 oC. (a) The total volume of the reaction mixture between FA 1 and FA 2 is constant. Explain why the temperature rise increases as more FA 1 is added to the mixture. As more FA 1 is added to the mixture, with amount of FA 2 being in excess (or FA 1 limiting), the number of moles of water produced in creases and amount of heat produced in creases in the presence of a same constant volume, hence the temperature rise increases. [1] (b) It is predicted that the maximum temperature change for the neutralisation would occur when t