VJC H2 Chem 2013 Prelim P2 QP

 VJC 2013 9647/02/PRELIM/13 [Turn over   2 Answer all the questions in the space provided. 1 Planning A student was provided with a spirit burner containing a ‘fuel mixture’ which was prepared by mixing equimolar amounts of hexane and ethanol. The enthalpy change of combustion of this ‘fuel mixture’ is 13.2 kJ per mole of ‘fuel mixture’. He was told to use the enthalpy change of combustion of this ‘fuel mixture’ to find the heat capacity of a metal calorimeter using the apparatus shown below. 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. Additional information: Specific capacity of water is 4.2 J cm3 K1 (a) Construct a balanced equation for the complete combustion of the ‘fuel mixture’ with state symbols. ………………………………………………………………………………………………… [1] (b) Identify two possible sources of error and suggest an improvement to overcome each of them in the experiment. Errors ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… Improvements ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… ………………………………………………………………………………………………… [3] spirit burner metal calorimeter 1490

 VJC 2013 9647/02/PRELIM/13 [Turn over   3 (c) Write a plan to determine the heat capacity of the metal calorimeter using the apparatus provided. In your plan you should give details of the procedure (number your steps) and provide a table to record the readings to be taken, including the units. [5] (d) Outline how you would determine the heat capacity of the metal calorimeter based on the plan that you have written and other information given in this question. [3] [Total: 12] 1491

 VJC 2013 9647/02/PRELIM/13 [Turn over   4 2 (a) World War I is sometimes known as 'the Chemists' War'. Knowledge of chemistry was applied towards developing high explosives and new methods of warfare such as the large scale use of poison gas. The first successful use of chlorine as a poison gas was at Ypres, Belgium, on 22 April 1915. 170 tonnes (1 tonne = 1000 kg) of chlorine contained in 5730 cylinders was released forming a grey-green cloud which drifted across French troops. Chlorine can damage the eyes, nose, throat and lungs and is fatal at concentrations of 1000 ppm and above (1 ppm = 1 mg dm −3). Early counter- measures to chlorine included instructing troops to cover their mouths with gauze pads soaked in sodium hydrogen carbonate solution. Eventually, more effective counter-measures to chlorine were developed and thus other poison gases were introduced. (i) Calculate the maximum amount of chlorine gas that could have been released from one of the cylinders that wa