A-LevelChemistryChemical energetics9701/12 · Oct/Nov 2012 · Q101 Mark
A student calculated the standard enthalpy change of formation of ethane, C2H6, using a method based on standard enthalpy changes of combustion. He used correct values for the standard enthalpy change of combustion of ethane (-1560 kJ mol¯¹) and hydrogen (–286 kJ mol¯¹) but he used an incorrect value for the standard enthalpy change of combustion of carbon. He then performed his calculation correctly. His final answer was –158 kJ mol¯¹. What did he use for the standard enthalpy change of combustion of carbon?
A–1432 kJ mol¯¹
B–860 kJ mol¯¹
C–430 kJ mol¯¹
D–272 kJ mol¯¹
✓ Correct answer
C: –430 kJ mol¯¹
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