My question is a general chemistry question that involves vapor pressure.

Question

The pressure under the surface of a liquid is given by P=pgh. Use this equation to calculate the height of the fluid column in a barometer that uses water instead of mercury.

Answer 1

Also -- the property concerned is pressure (hydrostatic), not vapor pressure. Unless you have a rather specialized barometer setup.

Remember also (is the question about this?) that there will be a vapor pressure of water acting (in the partial vacuum!) on the top of the column of liquid water. That will be dependent on temperature. Generally that correction is not applied, either to mercury, or to water, column barometer measurements, though it could be. The vaporization of water is what drives the water cycle on Earth; that's all passive (noone is sitting there boiling the tropical oceans). The vaporization of mercury is what drives mercury toxicity, in labs -- and why, for safety, mercury thermometers are generally replaced by thermocouple devices today.