NJC_H2_CHEM_P2_Question_Paper Prelim

NJC Preliminary Examination 9647/02/14 [Turn over NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 2 Structured Answer on the Question Paper. Additional Materials: Data Booklet 9647/02 Wednesday 3 Sept 2014 2 hours READ THE INSTRUCTIONS FIRST Write your subject class, registration number and name 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 paper clips, highlighters, glue or correction fluid. Answers all questions. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 /12 2 /16 3 /16 4 /17 5 /11 Total /72 This document consists of 15 printed pages and 1 blank page.

NJC Preliminary Examination 9647/02/14 2 For Examiner’s Use BLANK PAGE

3 NJC Preliminary Examination 9647/02/14 [Turn over For Examiner’s Use Answer all the questions. 1 Planning (P) A student was provided with a spirit burner. He was asked to determine the enthalpy change of combustion under laboratory conditions, H c, for ethanol using the following setup. Knowing that there could be significant heat loss arising from the above experimental setup, he decided to calibrate the calorimeter by burning 0.60 g of methanol (CH 3OH) to determine the calorimeter’s heat capacity, C calorimeter, which accounts for both the water and the copper can. Heat capacity is defined as the number of Joules of heat needed to raise the temperature of the calorimeter by one Kelvin or one degree Celsius. The temperature of the calorimeter rose from 25.0°C to 33.8°C. The same calorimeter was then used to measure the enthalpy of combustion of ethanol. (a) Given the enthalpy change of combustion of methanol is − 715 kJ mol –1, use the information above to calculate the heat capacity of the calorimeter, C calorimeter, stating its units. [2] calorimeter (copper can containing 50 cm3 of water) draught shield wick spirit burner containing selected alcohol stirrer lid thermometer

NJC Preliminary Examination 9647/02/14 4 For Examiner’s Use (b) Given the enthalpy change of combustion of ethanol is approximately −1370 kJ mol–1, calculate the minimum mass of ethanol required to give the same temperature change as that in the calibration. [2] (c) Write