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### Molar Heat Capacity

Posted: Thu Feb 07, 2019 9:04 pm
Why is molar heat capacity of an ideal gas greater at a constant pressure greater than at a constant volume?

### Re: Molar Heat Capacity

Posted: Thu Feb 07, 2019 10:07 pm
Molar heat capacity is greater at constant pressure than at constant volume because at constant P, some of the heat goes into expansion work which means there will be less energy left over to raise the temperature unlike at constant V, where no expansion work is done so all the energy goes into raising the temperature.

### Re: Molar Heat Capacity

Posted: Thu Feb 07, 2019 10:41 pm
The equation Cp = Cv + R shows us that the heat capacity at constant pressure is higher than the heat capacity at constant volume.

### Re: Molar Heat Capacity

Posted: Fri Feb 08, 2019 12:48 am
To expand on the previous two replies, the book gave the example of argon which has a constant volume heat capaccitg of 12.8, so when using the equation, you get 12.8 + 8.3= 21.1 for the constant pressure value. That is 65% greater than the constant volume value.