Edexcel Jan 2016 (IAL) Paper 1 Q20

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20 Compound X has the molecular formula C5H12. (a) Draw the displayed formulae of the three structural isomers of C5H12. (b) C5H12 reacts with chlorine to form a mixture of products. (i) Classify the type and mechanism of this reaction. (2) (2)(ii) Write the equations for the two propagation steps for this mechanism. Use the molecular formula, C5H12, in your first equation. Curly arrows are not required. D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A (2) (1) D O N O T W R I T E I N T H I S A R E A (iii) Write the equation for one termination step for this mechanism. Curly arrows are not required. 16 *P46937A01624*<br /> (c) An experiment was carried out to determine the enthalpy change of combustion of compound X, C5H12. 100.0 g of water was heated by burning 0.144 g of compound X. The temperature rise of the water was 14.5C. (i) Calculate the energy transferred, in kJ, in this experiment. Use the equation heat energy produced (J) = mass of water4.18temperature change (1) A E R A S I H T N I E T I R W T O N O D energy transferred =kJ (ii) Calculate the number of moles of compound X used in this experiment. (1) (iii) Calculate the enthalpy change of combustion of compound X. Include a sign and units in your answer. (2) moles of X =enthalpy change of combustion =A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D *P46937A01724* 17 Turn over<br /> (iv) The Data Book values for the enthalpy changes of combustion of the three structural isomers with the formula C5H12 are: 3509.1 kJ mol1 3503.4 kJ mol1 3492.5 kJ mol1 The experimental value calculated in (c)(iii) is very different from these values. Give two reasons, other than heat loss, for this large difference. (2)D O N O T W R I T E I N T H I S A R E A(v) Explain why it is not possible to deduce which of the isomers is compound X by comparing this experimental value and the Data Book values. (1)18 *P46937A01824* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br /> *(d) Complete the Hess cycle and use it to calculate the enthalpy change of combustion of C5H12 from the following data. Show all of your working. Standard enthalpy change of formation of C5H12(l) Standard enthalpy change of combustion of H2(g) Standard enthalpy change of combustion of carbon(s, graphite) 173.2 kJ mol1 285.8 kJ mol1 393.5 kJ mol1 (4) C5H12(l) + 8O2(g) 5CO2(g) + 6H2O(l)++A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D *P46937A01924* 19 Turn over (Total for Question 20 = 18 marks)<br />

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