Raoult's law vapour pressure calculator
The vapour pressure of the solution is the mole fraction of solvent times the vapour pressure of the pure solvent.
kPa
Vapour pressure of the solution
3.0115kPa
- Lowering
- 0.1585 kPa
- Relative lowering
- 5.000 %
Show the working
- Vapour pressure of pure solvent = 3.17
- Mole fraction of solvent = 0.95
- Vapour pressure of the solution = 3.17 * 0.95 = 3.0115
- Lowering = 3.17 - 3.0115 = 0.1585
- Relative lowering = 0.1585 / 3.17 * 100 = 5
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- P = x_solvent x P_pure
Water at 25 degrees Celsius has a vapour pressure of 3.17 kPa, which is the default here.