Convert For Helium Tank Conservation Of Mass Question ??

Conservation of mass question ?? - convert for helium tank

QUESTION:
Initially, 6 m ^ 3 contains helium rigid container (like an ideal gas) at 300 K and 0.10 MPa. The vessel is heated until the temperature reaches 400 K.

A safety valve at the top of the tank is opened when the pressure reaches 0.15 MPa, and the flow of helium, the prevention of pressure is greater than 0.15 MPa. Determine the final mass (kg) of helium in the tank.


My response:
Thus, in the hope that people do not believe you just posted here, without intending it, that's what I've done so far --

I could not really go to a way to use PV = nRT get a couple of times at the transformation. What I realized when I think, ** ** I have all the necessary for the state.

I only saw the state ofafter processing. You need to have the same V. And he tells us that P & T. I have V = 6 p =. 15 T = 400 Since the problem is described, it seems that the final state. No, I calculate that using PV = nRT kg and was honored for his urn.

Thoughts?