The difference between the heats of a reaction at constant pressure and volume for the reaction 2C6H6(l)+15O2(g)→12CO2(g)+6H2O(l) at 25°C in kJ is:
A
−7.43kJ
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B
−4.43kJ
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C
−1.43kJ
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D
None of the above
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Solution
The correct option is A−7.43kJ △H−△U = △nRT △n = Number of moles of gaseous products − number of moles of gaseous reactants. △n = 12−15 = −3 △H is change in enthalpy △U is change in internal energy
Substituting the respective values, △H−△U=−3×8.314×298=−7.43kJ