## Does the substance make a difference in expansion work?

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

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

### Does the substance make a difference in expansion work?

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."

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

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

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?

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