Colligative Properties Calculator: Boiling Point Elevation, Freezing Point Depression, Osmotic Pressure and Raoult's Law
How a dissolved solute changes boiling, freezing, osmosis and vapour pressure.
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How this calculator works
Choose the solvent and enter the mass and molar mass of the solute and the mass of the solvent.
Enter the van't Hoff factor: 1 for sugar, 2 for salt.
The calculator gives the molality, the new boiling and freezing points, the osmotic pressure and the vapour pressure.
Formulas used
- \Delta T_b = iK_bb
- \Delta T_f = iK_fb
- \Pi = icRT
- P = x_{solvent}P_0
Worked example
With the default numbers in the calculator above:
- Moles of solute and the molality (moles of solute per kg of solvent): 0.277531 mol/kg (0.0555062 mol of solute)
- Boiling point elevation: 0.1421 K (the solution boils at 100.142 C)
- Freezing point depression: 0.51621 K (the solution freezes at -0.516208 C)
- Osmotic pressure: 687.99 kPa (6.79 atm)
- Vapour pressure of the solution (Raoult's law: mole fraction of solvent times the pure vapour pressure): 3.15423 kPa, a lowering of 0.01577 kPa
Change the numbers in the calculator to see the full working, every step, for your own case.
Common questions
What is a colligative property?
A property that depends on how many particles are dissolved, not on what they are.
What is the van't Hoff factor?
The number of particles one formula unit makes in solution: 1 for glucose, 2 for NaCl, 3 for CaCl2.
Why is salt put on icy roads?
The dissolved salt lowers the freezing point of the water, so the ice melts at a temperature below 0 C.
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Got a question about this? Ask an engineering question and get a plain-language answer with references.
Further reading: Any first-year chemistry text (colligative properties).
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