OCR A Jun 2011 Paper 2 Q1

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Answer all the questions. 1 Many organisms use the aerobic respiration of glucose, C6H12O6, to release useful energy. (a) The overall equation for aerobic respiration is the same as for the complete combustion of C6H12O6. (i) Write the equation for the aerobic respiration of C6H12O6.[1] (ii) Explain, in terms of bond breaking and bond forming, why this reaction is exothermic.[2] (b) The table shows some enthalpy changes of combustion, Hc. substance Hc / kJ mol1 C(s) H2(g) C6H12O6(s) 394 286 2801 (i) What is meant by the term enthalpy change of combustion, Hc?[2]OCR 2011<br />
 (ii) The enthalpy change of formation, Hf , of glucose, C6H12O6, cannot be determined directly. The equation for this enthalpy change is shown below. 6C(s) + 6H2(g) + 3O2(g) C6H12O6(s) Suggest why the enthalpy change of formation of C6H12O6 cannot be determined directly.[1] (iii) Use the Hc values in the table to calculate the enthalpy change of formation of C6H12O6. Hf =kJ mol1 [3] [Total: 9]OCR 2011 Turn over<br />

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