Dalton's Law of Partial Pressures

Question

Two gases are contained in gas bulbs connected by a valve. Gas A is present in a 1 L bulb at a pressure of 818 torr. Gas B exerts a pressure 328 torr in a 1 liter bulb. The valve is opened and the two gases come to equilibrium. What is the partial pressure of gas A after equilibrium has been established, reported to the nearest whole number.

Answer 1

For gas A: V₁ = 1.0 L P₁ = 818 torr after the valve is opened, the total volume V₂ = 2.0 L P₂ = ?

Use Boyle's law P₁V₁ = P₂ V₂ 818 torr x 1.0 L = 2.0 L x P₂ P₂ = 409 torr at equilibrium

Answer 2

For gas A, it begins at a pressure of 818 torr in a volume of 1 L. At the end of the experiment it is now in a volume of 2 liter after the valve is opened. The question is essentially asking what is the new pressure of gas A.

P₁V₁ = P₂V₂

P_{2 =} P₁V₁/V₂

P₂ = (818 torr)(1 L)/2 L = 409 torr <— partial pressure of gas A