ChemistryPhysical ChemistryA-Level
AQAAPIBBachilleratoCBSECCEACESSCISCE

Osmotic pressure Calculator

Relate osmotic pressure to concentration and temperature.

Use the free calculatorCheck the variablesOpen the advanced solver
Open Advanced Calculator
This is the free calculator preview. Advanced walkthroughs stay in the app.
Result
Ready
Osmotic Pressure

Formula first

Overview

Osmotic pressure is the hydrostatic pressure required to halt the net flow of solvent across a semipermeable membrane into a more concentrated solution. As a colligative property, it depends solely on the number of solute particles present in the solution, regardless of their chemical identity.

Symbols

Variables

i = van 't Hoff factor, C = Concentration, R = Gas Constant, T = Temperature, \Pi = Osmotic Pressure

van 't Hoff factor
Concentration
Gas Constant
Temperature
Osmotic Pressure

Apply it well

When To Use

When to use: Apply this equation when analyzing dilute solutions where the solute behaves ideally. It is the primary tool for determining the molar mass of large macromolecules, like proteins or polymers, and for calculating the isotonicity of biological fluids.

Why it matters: Osmotic pressure is vital for maintaining cellular integrity and drives essential biological processes such as water uptake in plant roots. In industry, understanding this pressure is critical for desalination via reverse osmosis and the development of safe intravenous medications.

Avoid these traps

Common Mistakes

  • Forgetting the van't Hoff factor for electrolytes.
  • Using wrong R units.

One free problem

Practice Problem

A biochemist prepares a 0.50 M solution of glucose (a non-electrolyte) at a lab temperature of 298.15 K. Calculate the osmotic pressure (Pi) in atmospheres.

van 't Hoff factor1
Concentration0.5 mol/dm^3
Gas Constant0.08206 dm^3·bar/mol·K
Temperature298.15 K

Solve for:

Hint: Since glucose does not ionize in water, the van't Hoff factor is exactly 1.

The full worked solution stays in the interactive walkthrough.

References

Sources

  1. Atkins' Physical Chemistry
  2. IUPAC Gold Book: Osmotic pressure
  3. Wikipedia: Osmotic pressure
  4. Bird, Stewart, Lightfood - Transport Phenomena
  5. NIST CODATA
  6. IUPAC Gold Book
  7. Atkins' Physical Chemistry (11th ed.)
  8. Halliday, Resnick, and Walker, Fundamentals of Physics (11th ed.)