Problem 5-95

According to Dalton's law of partial pressure, P of a gas containing several gases, is equivalent to the sum of the pressures (partial) of all the gases present.

P_total = P(H₂) + P(N₂)

However, in this problem, the partial pressures of each gas cannot be simply added together because their volumes are not the same.

The sum of all partial pressures can be calculated if all gases occupy the same volume, i.e. when the shut-off valve is open or 3.00 L :

Since PV = nRT, therefore P₁V₁ = P₂V₂:

P(H2) = 475 torr ×	2.00 L	= 316.6 torr
	3.00 L

P(O2) = 0.200 atm × 760 torr/atm ×	1.00 L	= 50.7 torr
	3.00 L

Finally: P_total = P(H₂) + P(N₂)= 367 torr.