# Isothermal expansion hw problem

1. Nov 28, 2006

Suppose 145 moles of a monatomic ideal gas undergo an isothermal expansion from 1.00m^3 to 4.00m^3, as shown in figure. what is the temp at the beginning and end of this process? how much work is done by the gas during the expansion?

http://www.physics.brocku.ca/Courses/1p23/images/FG18_24.JPG [Broken]

since it is isothermal the temperature is constant correct?
so to solve for the temperature would i just use pv=nrt with the respective values for pressure and volume?
and for the work done W=nrtln(vf/vi)

thanks

Last edited by a moderator: May 2, 2017
2. Nov 28, 2006

### KoGs

You have p_i and p_f, and also v_i and v_f. Can you think of a formula that uses p and v ?

Hint: What are the units for pressure?

3. Nov 28, 2006

so i wouldnt use pv=nrt?

4. Nov 28, 2006

### KoGs

Try it out. Plug in the values of p_i and v_i into that formula.
Then plug in the values of p_f and v_f into that formula.
See what you get.

5. Nov 28, 2006

im getting .332 for the temperature.

6. Nov 28, 2006

and for the work i get 1670.42j

7. Nov 28, 2006

### KoGs

Now you tell me. Is temperature constant?

8. Nov 28, 2006

yup yup. thought it was tryin to trick me by askin the temp of beginnin and end like it was gonna be two different values.