## HW 8.31

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### HW 8.31

For part a, the pressure is held constant. I know we are multiplying by the number of moles of Kr by the change in temperature but i just don't understand where they are getting the rest. When I checked the solution manual for part a, they were multiplying the change in temperature by the number of moles by 20.8 J/g C. Could someone explain why they used that number? and how we are supposed to find it?

Humza_Khan_2J
Posts: 56
Joined: Thu Jul 13, 2017 3:00 am

### Re: HW 8.31

Within the text(and the equation sheet on Prof. Lavelle's website), we can find that the olar heat capacity of a monoatomic ideal gas at constant pressure to be 5/2R. Since R is 8.314, 5/2R is the 20.8 J/gC you were looking for.

104922499 1F
Posts: 53
Joined: Fri Sep 29, 2017 7:04 am

### Re: HW 8.31

will there be a question similar to this on the test?

Jennie Fox 1D
Posts: 66
Joined: Sat Jul 22, 2017 3:01 am

### Re: HW 8.31

For this question, you would use q=mC(delta)T. For part a, where the pressure is held constant (Cp), C would be equal to (5/2)R, where R=8.314. In part b, where the volume is held constant (Cv), C would be equal to (3/2)R, where R is also 8.314. So basically, you would just replace the "C"s in q=mC(delta)T with either (5/2)R at a constant pressure or (3/2)R at a constant volume.

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