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Grade 12Physical Chemistry

The difference between heats of reaction at constant pressure and constant volume for the reaction

2C6H6 (I) + 1502(g) 12CO2 (g) + 6H2O (I)

at 25?C in kJ mol-1 is

1)

-7.43


2)

+3.72


3)

-3.72


4)

+7.43

Profile image of Pratik Sharma
16 Years agoGrade 12
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2 Answers

Profile image of Askiitians Expert Sahil Arora - IITD
16 Years ago

Dear Student,

Heat of reaction at constant pressure is ΔH and at constant volume is ΔU.

ΔH-ΔU=ΔngRT

Δng=12-15=-3

ΔngRT=(-3)*(8.314*10-3KJ/mol/K)*(298 K)=-7.43

one more thing,someone may think of dividing the reaction by 2..but that will be wrong.

On multiplying by a factor,ΔH and ΔU also get multiplied by the factor..

All the best Pratik !!!




Regards,

Askiitians Experts

Sahil Arora
Profile image of Saurabh Kumawat
7 Years ago
2C6H6(l)+15O2(g) -> 12CO2(g)+6H2O(l) at 25℃ in KJ/mol
∆H-∆U=∆ngRT
∆ng=12-15=-3
∆ngRT=(-3)×(8.314×10^-3KJ/mol/K)×298=-7.43