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Osmotic Pressure Calculator.

Calculate ideal dilute-solution osmotic pressure with the van't Hoff equation.

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Osmotic pressure: 2.44654 atm

Osmotic pressure

2.446540atm

Educational arithmetic only. Keep units consistent and use measured or explicitly supplied chemistry inputs; this tool does not infer reaction pathways, property tables, or safety guidance.

Use Cases

Estimate osmotic pressure in lab solutions

Quickly compute osmotic pressure for dilute solutions in chemistry experiments, helping to predict solvent flow across semipermeable membranes.

Example: For 0.1 M NaCl at 298 K, i=2, osmotic pressure ≈ 4.89 atm.

Educational practice for colligative properties

Students can verify textbook problems and understand how concentration, temperature, and dissociation affect osmotic pressure.

Example: Calculate osmotic pressure of 0.5 M glucose at 310 K (i=1) ≈ 12.7 atm.

Frequently Asked Questions

What is the van't Hoff equation for osmotic pressure?
The van't Hoff equation is Π = iMRT, where Π is osmotic pressure, i is the van't Hoff factor, M is molarity (mol/L), R is the ideal gas constant (0.0821 L·atm/(mol·K)), and T is temperature in Kelvin.
What is the van't Hoff factor (i)?
The van't Hoff factor (i) is the number of particles a solute dissociates into in solution. For non-electrolytes, i = 1. For strong electrolytes, i equals the number of ions per formula unit (e.g., NaCl gives i = 2).
Why must temperature be in Kelvin?
The van't Hoff equation uses the ideal gas constant R, which requires temperature in Kelvin. Celsius or Fahrenheit would give incorrect results. To convert, add 273.15 to Celsius.

Tips & Common Mistakes

Tips

  • Ensure molarity is in mol/L; if you have molality, convert using solution density.
  • Use the correct van't Hoff factor: for weak electrolytes, it may be less than the number of ions due to incomplete dissociation.
  • Temperature must be in Kelvin; add 273.15 to Celsius.
  • This calculator assumes ideal dilute solutions; for concentrated solutions, results may deviate.

Common Mistakes to Avoid

  • Using Celsius instead of Kelvin for temperature.
  • Forgetting to multiply by the van't Hoff factor for ionic compounds.
  • Using molality instead of molarity without conversion.

Last updated: August 13, 2026