Raoult's Law Calculator
🧪 Solutions & Molarity. Use the Raoult's law formula to find vapour pressure, solvent mole fraction, pure solvent pressure: pick the value you want, type the others, and the answer updates as you go.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Vapour pressure | kPa |
| Solvent mole fraction | no unit |
| Pure solvent pressure | kPa |
Worked example
Find the vapour pressure when Solvent mole fraction = 0.93, Pure solvent pressure = 3.17 kPa.
Using Psolution = Xsolvent P°solvent: Vapour pressure = 2.9481 kPa.
Frequently asked questions
What is the formula for Raoult's law?
Psolution = Xsolvent P°solvent.
What do the letters stand for, and what units are used?
Vapour pressure in kPa, Solvent mole fraction, Pure solvent pressure in kPa.
How do you calculate vapour pressure?
Put the values into Psolution = Xsolvent P°solvent. For example, with Solvent mole fraction = 0.93, Pure solvent pressure = 3.17 kPa, vapour pressure = 2.9481 kPa.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (vapour pressure, solvent mole fraction, pure solvent pressure) and fill in the others: it rearranges the formula for you.
