What causes waters low vapor pressure?
Water molecules hydrogen bond which is a very strong intermolecular force. As a result the water molecules are held together well. Vapor pressure is dependent on how well molecules are intermolecularly bonded to one another. If a substance like water is held together well then it will have a low vapor pressure because a larger amount of energy is required to break these intermolecular bonds. Compare water to carbon tetrachloride which is non polar and can’t hydrogen bond. Because it only has weak London dispersion forces to hold the molecules together it will have a higher vapor pressure. This is because only a small amount of energy is required to break the intermolecular bonds causing the CCl4 to vaporize.
