## Practice Quiz #3

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

Michael Lonsway 3O
Posts: 43
Joined: Wed Sep 21, 2016 2:57 pm

### Practice Quiz #3

If 2.00 mol of an ideal gas at 300. K and 3.00 atm expands isothermally and reversible from 6.00L to 18.00L and has a final pressure of 1.20 atm, what is w, q, and delta U?

The answer key said that delta U is 0 but would it still be 0 if we weren't working with an ideal gas? Also what initial conditions would cause q, w, or delta U to be 0?

Audrey_Hall_2I
Posts: 17
Joined: Wed Sep 21, 2016 2:56 pm

### Re: Practice Quiz #3

Also are we supposed to be able to solve this and get numerical answers or is it conceptual?

Michael Lonsway 3O
Posts: 43
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Practice Quiz #3

You need to solve this problem numerically but I was also wondering the concept behind when u, q, or w would be 0.

Chem_Mod
Posts: 18023
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 418 times

### Re: Practice Quiz #3

$\Delta U = 0$ when it is an ideal gas and isothermal.

I'm not fully sure if the conditions were with a gas that was not an ideal gas that $\Delta U = 0$.

As for the rest;

w = 0, when the volume is constant, because of $w=-P\Delta V$

q is generally not zero too many times except for when the whole system needs to sum to zero such as when the system is isolated.