Given the following, what is the pressure of dry hydrogen gas if the vapor pressure of water at 25°C is 3.8 mm Hg?

Hydrogen gas produced in the laboratory by the reaction of zinc and hydrochloric acid as collected over water at 25°C. The barometric pressure at the time was 742.5 mm Hg.

1 Answer
Nov 6, 2016

PTotal=PGas+PSVP=742 mm Hg

Explanation:

And PSVP is the so called saturated vapour pressure, which for this experiment = 3.8 mm Hg

So Pdihydrogen = 742 mm Hg 3.8 mm Hg = 738.2 mm Hg.

Note that here the quoted value of PSVP is wrong. I suspect that they got confused with respect to a pressure measurement in mm Hg and Pascal.

The vapour pressure of water at 298K is 24 mm Hg.