the vapor pressure of water at 20.0C is 17.5mm Hg.?

Question

If the pressure of the gas collected over water was measured to be 453.0mm Hg, what is the pressure of the pure gas?

Answer 1

Since we are assuming equilibrium, the partial pressure of H20 vapor is 17.5 mm, and so the partial pressure of the rest of the gas is 435.5 mm Hg.