13147 14 The standard enthalpy of combustion of ethane can be estimated using average bond enthalpies. (a) Define the following terms: (i) standard enthalpy of combustion [2] (ii) average bond enthalpy [2] (b) Suggest why the bond enthalpy value for O O is not an average value. [1] 13147 [Turn over (c) The complete combustion of ethane can be represented by the equation: 2C2H6 + 7O2 → 4CO2 + 6H2O Use the bond enthalpies in the table below to calculate the standard enthalpy of combustion for ethane. Bond Bond enthalpy /kJ mol-1 C H 413 C C 348 O O 497 C O 803 O H 464 [4] (d) Suggest why a mixture of ethane and oxygen is stable at room temperature and does not react to form carbon dioxide and water. [1]
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This question is part of the UK A-Level Chemistry syllabus. In the actual exam, structured questions typically require linking specific keywords to gain full marks. Applaa helps you drill these topics.
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