Finding the amount of heat required to double volume?

1. May 8, 2012

charmedbeauty

1. The problem statement, all variables and given/known data

In an experiment, 1.35 mol of oxygen (02) are heated at constant pressure starting at 11.0°C. How much heat must be added to the gas to double its volume? You may assume without proof, that the molar specific heats are cp=7R/2 and cv=5R/2.

2. Relevant equations

3. The attempt at a solution

My working so far...

Q=nCpΔT

Q=n(7R/2)ΔT

Q= 1.35(7R/2)(s-11) -----> where s= Tf

But I need some equation linking change in volume to this....

ie Q= -PΔV

But I dont Know what P is?

Perhaps I need something with ΔEint but im not to sure.
I was thinking I will need to solve the first equation simultaneously with one with ΔV

I'm stuck as to where to go from here??