If two moles of aluminum chloride are dissolved in two liters of water, how does the vapor pressure of the water change?
it decreases because nonvolatile aluminum and chloride ions now occupy some of the volume of the system and this reduces the volume of the volatile solvent particles that cause vapor pressure.
it does not change because the amount of water in the system remains constant in both systems and water is the only volatile compound in this system.
it increases because aluminum and chloride ions displace water molecules, which escape into the gas phase. this increases the number of vapor particles, increasing vapor pressure.