Chemistry Question -- Opening a valve between two containers....

[Physicsnoob90]

Homework Statement

Two closes containers are connected by a valve, which initially separates the containers from each other. C
Container A has 8.00 L of H2 at 3.00 atm and temperature 400 k.
Container B has 6.00 L of O2 at 4.00 atm and temperature 400 k

The valve is opened, the gases mix, and they then react to form H2O. (temperature for both stay the same)
Find the moles of each gases before the valve is opened.

Homework Equations

Chemical formula: 2 H2 (g) + O2 (g) === 2 H2O (g)

The Attempt at a Solution

for H2: PV/ RT , (3.00 atm) (8.00 L) / (0.0821 (L atm/ mol k)) (400 k) = 0.731 mol H2

I also got the same moles for O2, but i feel like i did something wrong. Can anyone help me?

 

[Borek]

You did OK, the part about the reaction is irrelevant to the system before the valve was open.