Last updated: March 2, 2026

Understanding Osmotic Pressure

Formula

Osmotic pressure is the minimum pressure needed to prevent solvent from flowing through a semipermeable membrane from a dilute to a concentrated solution. It is a colligative property fundamental to biology, medicine, and chemical engineering.

The van't Hoff equation π = iMRT calculates osmotic pressure from the solution's molarity, temperature, and the number of dissolved particles. It is structurally identical to the ideal gas law.

Common use cases:

  • Reverse osmosis water purification
  • IV solution formulation
  • Molar mass determination of polymers

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