How do you calculate the vapor pressure of a solution?
This is done by using Raoult's law, which states that, for an ideal solution, the partial vapor pressure of a component in that solution is equal to the mole fraction of that component multiplied by its vapor pressure when pure.
If you're dealing with a solution that has a non-volatile solute (a solute that does not have the tendency to form vapor at the temperature of the solution), then the vapor pressure of that solution is
If however you're dealing with a solution that contains a volatile solute, the vapor pressure of that solution is
This equation can be extended to solutions containing three or more components.