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At 300 K, the standard enthalpies of formation of `C_(6)H_(5)COOH (s), CO_(2)(g)` & `H_(2)O (l)` are , `-408, -393` & `-286" kJ mol"^(-1)` respectively. Calculate the heat of combustion of benzoic acid at : (i) constant pressure (ii) constant volume. |
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Answer» Correct Answer - (i) -3201 kJ/mol (ii) -3199.75 kJ/mol `C_(6)H_(5)COOH+15/2 O_(2) rarr 7CO_(2)+3H_(2)O(l)` `DeltaH=(7xx-393)+3(-286)-(408)=-3201` `DeltaU=DeltaH-Deltan_(g) RT` `Deltan_(g)=-1/2` `DeltaU=-3199.75 kJ mol^(-1)` |
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