Does the substance make a difference in expansion work?


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nicolely2F
Posts: 149
Joined: Sat Sep 14, 2019 12:17 am

Does the substance make a difference in expansion work?

Postby nicolely2F » Tue Feb 11, 2020 9:57 pm

Some exercises specify a gas that is being compressed by a piston and I don't know whether knowing what gas it is (and therefore its properties, like molar mass) is important for solving the exercise. One example is:

"Given a piston that expands from 0.200 L to 1.50 L, at 25 C, and is filled with 0.18 moles of CH4, what is the amount of work done at a constant pressure of 3.56 atm? Express answer in units of Joules."

I'm not sure how to go about this and where to use 0.18 of CH4.

connie 2C
Posts: 106
Joined: Thu Jul 11, 2019 12:17 am

Re: Does the substance make a difference in expansion work?

Postby connie 2C » Wed Feb 12, 2020 11:33 am

im not sure if you need to use the moles of gas given in this equation because there is a change in volume and the question gives you a constant external force. since those two things are given, you can use w=-P*deltaV to calculate the work done. you would then use the conversion factor to change the units L*atm to J. where did this question come from?

nicolely2F
Posts: 149
Joined: Sat Sep 14, 2019 12:17 am

Re: Does the substance make a difference in expansion work?

Postby nicolely2F » Wed Feb 12, 2020 11:39 am

That was what I thought, but I wasn't sure. Thanks!
I got this from one of Lyndon's help sessions worksheet.


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