The standard enthalpy of formation of octane (C8H18) is −250kJ/mol. Calculate the enthalpy of combustion of C8H18.
Given : enthalpy of formation of CO2(g) and H2O(l) are −394kJ/mol and −286kJ/mol respectively:
A
−5200kJ/mol
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B
−5726kJ/mol
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C
−5476kJ/mol
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D
−5310kJ/mol
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Solution
The correct option is C−5476kJ/mol C8H18(g)+252O2(g)→8CO2(g)+9H2O(l)ΔrH∘=8×(−394)+9×(−286)−(−250)=−5476kJ/mol