Posted by Kristine on .
A flask has 1.00 L of O2 (g) at STP (the amount of gas and volume are held constant, P=1 bar) and the second has 1.00 L of O2 at 100 C. What mass of O2 must release if we get the pressure to remain at 1.00 bar when it's heated to 100 C?
Can someone please explain how to do this? What i tried to do was calculate the n of the first flask at STP. I got .00403mol. I then calculated the n of the second flask using n(initial)T(initial)/T(final)
I'm not sure where to go from here. I'm also not sure whether I calculated it correctly. Any help would be appreciated, thank you

Chemistry 
DrBob222,
I may have missed something but I don't know what the second flask has to do with the problem. I would use PV = nRT and solve for mols in the first flask. Then use PV = nRT but this time with 100 C, then subtract the two n values.