# How to solve this problem?

1. Nov 5, 2009

### sowmit

1. The problem statement, all variables and given/known data
A sample of helium behaves as an ideal gas as it heated at a constant pressure from 273k to 373 k. If 20.0 J of work is done by the gas during this process, what is mass of helium present?

2. Relevant equations

I was thinking about pv=nRt, but not sure.

3. The attempt at a solution
Ti= 273k, Tf= 373K, Q=20.0J, P=1atm, m=?

Ugghh, how do I solve this? Anyone?

2. Nov 6, 2009

### clamtrox

The thermodynamic quantity, that tells how how much energy you need for one degree change in temperature, is called heat capacity.

For solving the heat capacity, you might be able to use the fact that for ideal gases, $$p = \frac{2E}{3V}$$.

Last edited: Nov 6, 2009
3. Nov 6, 2009

### mikelepore

There's an expression for the work done by an ideal gas in expanding, a expression which applies specifically when the pressure is constant. From this you can calculate the number of moles.