Osmotic Pressure Calculator
Π = iMRT, and the figures are larger than you expect.
Work out Osmotic Pressure. Π = iMRT, and the figures are larger than you expect. Shows the working, not just the answer.
Osmotic pressure (atm)
24.4654
24.7896 bar · 2,478.957 kPa
Π = iMRT, which is the ideal gas law with concentration in place of n/V. The figures are larger than intuition suggests: a 1 M solution at 25 °C exerts about 24.5 atmospheres, which is why reverse osmosis needs industrial pumps and why a cell placed in pure water bursts rather than merely swelling.
How the Osmotic Pressure Calculator works
Osmotic pressure is the ideal gas law with concentration in place of n/V. The figures surprise people: a 1 M solution at 25 °C exerts about 24.5 atmospheres, which is why reverse osmosis needs industrial pumps.
Also known as: osmolarity calculator · van t hoff osmotic equation · reverse osmosis pressure calculator · how to calculate osmotic pressure
Frequently asked questions
How do I calculate osmotic pressure?
Π = iMRT, with the temperature in kelvin. A 1 M solution at 25 °C gives about 24.5 atm.
Why is it so high?
Because a mole per litre is a great many particles. The same arithmetic that gives a gas 22.4 litres per mole at STP gives a solution tens of atmospheres of osmotic pressure.
What is reverse osmosis?
Applying pressure above the osmotic pressure to push solvent the wrong way through a membrane. Seawater's osmotic pressure is around 27 atm, so desalination plants work well above that.
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