Work out vapour pressure (raoult law) instantly with clear inputs, formula shown and shareable results.
Raoult's law states that the vapour pressure above an ideal solution is the pure solvent's vapour pressure scaled by the solvent's mole fraction. A non-volatile solute contributes no vapour of its own, so it simply dilutes the solvent at the surface. Water at 25 C (23.8 mmHg) with 1 mol of solute per 10 mol of water drops to 21.6 mmHg, a lowering of 2.16 mmHg.
Raoult's law
P(solution) = x(solvent) x P0(solvent)
Lowering
dP = P0 - P = x(solute) x P0
Solute particles occupy part of the surface, so fewer solvent molecules can escape per second while condensation is unchanged. Equilibrium settles at a lower pressure.
Then each component contributes its own partial pressure by Raoult's law and the total is their sum. This calculator assumes a non-volatile solute.