How Do Initial Pressures Compare in Two Heated Monatomic Gas Containers?

[Kites]

Homework Statement

Two 800 cm^3 containers hold identical amounts of a monatomic gas at 20 C. Container A is rigid. Container B has a 100 cm^2 piston with a mass of 10 kg that can slide up and down vertically without friction. Both containers are placed on identical heaters and heated for equal amounts of time.

What are the initial pressures in each container?

Homework Equations

PV = nRT
Q = nC*(delta)T
W = - p*(delta)Volume

The Attempt at a Solution

I've no idea. I've worked on this for 3 hours and I feel that I have two unknowns so far. I want to know the pressure in one of the containers, say V_1 for cylinder one.

So...

P = n*R*T/V_1

But how do I find the moles of this gas? And if that's not needed, what can I possibly do to fix this? I must be missing something obvious.

 

[denverdoc]

I believe you're right, that the pressure in the first container cannot be known from the info given. My guess is this is an oversight, and the assumption is that it is 1atm, because the interesting part of the problem has to do with the piston. So if you assume 1atm initially can you compute the pressure of the second vessel when the piston is in its equilibrium position?