Why is the air pressure of dry air higher than the air pressure of wet air?

Water vapor is a gas made up of hydrogen and oxygen (H2O). Dry air is mostly nitrogen and oxygen. Nitrogen is heavier than water vapor so when you mix dry air and water vapor, the mixture is less dense.

Wet air is a mixture of dry air and water vapour.Water vapour is a gas lighter than dry air.It has been found out that,the specific gravity of water vapour as compared with that of dry air,at the same temperature and pressure is 0.6221 or 5/8 for all practical purposes.That means the density of water vapour is 5/8 of the density of dry air.So ,a mixture of dry air and water vapour (which is the moist or wet air) will be lighter than the dry air for the same volume.

Air pressure is the weight of the air column per unit area over a place,the lighter wet air exerts less pressure than the dry air.So,the pressure of dry air is higher.

if you look it up on a periodic table, the atomic mass of O2 (which makes up the dry air) should be higher than the mass of H2O (water vapor). umm.. i think.

You can get more air into an empty glass than you can one that is full of water.

i think because it has more mass in the air.