An experiment is conducted in which a quantity of H2(g) is chemically generated in a closed headspace of volume V1 at absolute temperature T1, thereby raising the total pressure from P0 (the initial air pressure) to P1 (the total final pressure of H2(g) + air).
Compose an algebraic expression for the volume (V2) that this sample of H2(g) would occupy if it were isolated (pure -- i.e. no air) at absolute temperature T2 and partial pressure P2.

V2 = V1*T2/T1*(P1-P0)/P2

Now, suppose that the above experiment generated n mol of H2(g), that T2 = 0 °C and that P2 = 1 atm. Give the simple algebraic expression, in terms of V2 and n, which equates to the molar volume of H2(g) at STP.

VM = V2/n