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Thermodynamics

Question
CBSEENCH11006038

Calculate the difference between heats of reaction at constant pressure and constant volume for the reaction:
space 2 straight C subscript 6 straight H subscript 6 left parenthesis straight I right parenthesis space plus space 15 straight O subscript 2 left parenthesis straight g right parenthesis space rightwards arrow space space 12 CO subscript 2 left parenthesis straight g right parenthesis space plus space 6 straight H subscript 2 straight O left parenthesis straight I right parenthesis at 25 degree straight C space in space kJ.

Solution
increment straight H space equals increment straight U space plus space increment straight n subscript straight g RT
therefore space space increment straight H space minus space increment straight U space equals space increment straight n subscript straight g RT
space space space space space space space space space space space increment straight n subscript straight g space equals space 12 minus 15 space equals space minus 3
therefore space space space increment straight H space minus space increment straight U space equals space left parenthesis negative 3 right parenthesis thin space left parenthesis 8.31 right parenthesis space cross times space 298 space equals space minus 7.43 space kJ