If the vapor pressure of water is 21.1 mm Hg at the collection temperature, what is the pressure of the collected gas?

Question

Suppose you are collecting a gas over water at 23 ^oC and obtain a pressure reading of 794.5 mm Hg.

If the vapor pressure of water is 21.1 mm Hg at the collection temperature, what is the pressure of the collected gas?

Answer 1

Subtract the vapor pressure of water (21.1 mm Hg) from the total pressure (794.5 mm Hg) to obtain the pressure of the gas alone.