CIE Jun 2013 v3 Paper 3 Q1

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Examiners For Use You are to determine the enthalpy change of the reaction between hydrochloric acid and sodium hydroxide by adding various volumes of acid and alkali and measuring the change in temperature. FA 1 is 0.950 mol dm3 hydrochloric acid, HCl. FA 2 is aqueous sodium hydroxide, NaOH. (a) MethodSupport the plastic cup in a 250 cm3 beaker. Using a measuring cylinder, transfer 25 cm3 of FA 1 into the cup and measure the temperature of the acid. Tilt the cup if necessary to cover the bulb of the thermometer. Record this initial temperature. initial temperature of FA 1 =C Use a second measuring cylinder to transfer 10 cm3 of FA 2 and 25 cm3 of water into a 100 cm3 beaker. Add this mixture to the plastic cup and stir. Measure the maximum temperature reached and record this maximum temperature in the table below. Rinse out the plastic cup and shake it to remove excess water. Repeat the experiment, using the volumes of FA 1, FA 2 and water shown in the table. Record the maximum temperature for each experiment. volume FA 1 / cm3 volume FA 2 / cm3 volume water / cm3 maximum temperature / C 25 25 25 25 25 25 10 15 20 25 30 35 25 20 15 10 5 0 You are going to plot a graph using these results tond the volume of FA 2 that gives the greatest maximum temperature. Before you plot the graph, choose two further volumes of FA 2 that will allow you tond more precisely the volume that gives the greatest maximum temperature. Record the volumes you choose, carry out the experiments and record the corresponding [2] maximum temperatures, in the table.UCLES 2013 9701/33/M/J/13<br /> (b) (i) On the grid below, plot the maximum temperature on the y-axis against the volume of FA 2 on the x-axis. Examiners For Use (ii) Draw two straight lines of bestt on your graph, one to show where the temperature was increasing and the other after the greatest maximum temperature had been reached. (iii) Using your graph and the initial temperature recorded in (a), determine the maximum temperature change that could occur when 25 cm3 of FA 1 react with FA 2. maximum temperature change =C [5]UCLES 2013 9701/33/M/J/13 [Turn over<br /> Examiners For Use (c) Calculation (i) Calculate the energy needed to produce the temperature change in (b)(iii). (Assume that 4.3 J of heat energy changes the temperature of 1.0 cm3 of solution by 1.0 C.) (ii) Calculate the number of moles of HCl used in each experiment. energy needed =J (iii) Calculate the enthalpy change, in kJ mol1, when 1 mole of HCl reacts with NaOH. moles of HCl =mol enthalpy change =kJ mol1 [3] (value) (sign) [Total: 10]UCLES 2013 9701/33/M/J/13<br />

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