|MadSci Network: Chemistry|
If a gas is collected over water, all textbooks show the pressure correction by subtracting the vapor pressure of water. But why no volume correction? The water vapor that is present is responsible for some of the volume that is occupied. The gas that is of interest would occupy a smaller volume if not for the water vapor. This would give a smaller answer when we use n = PV/RT. This is complicated because we can't get the # of mols of water vapor present from the info usually given in the problems.
Re: Why don't we make a volume correction when a gas is collected over water?
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