physics
posted by reeta .
A 2.10 mol sample of oxygen gas is confined to a 5.10 L vessel at a pressure of 7.99 atm. Find the average translational kinetic energy of an oxygen molecule under these conditions in (j/mol)
When i was working this out i tried using pv=nrt to find the temperature which i got was 275 K.
I the tried usingg K TotTrans=3/2nRT
3/2(2.10mol)(8.31J/mol)(275K)=7.20x10^3 J/mol. This was not the right answer however, help please.

Where did 3/2 nRT come from?
Ktrans=3/2 kT where k is boltzmann's constant.
So find Temp with pV=nRT, then find 3/2 kT