Osmotic Pressure Calculator

To calculate Osmotic Pressure, input Solute Concentration (in mol/L), Temperature (in Kelvin or Celsius), and Van’t Hoff Factor in calculator. The calculator will compute Osmotic Pressure in various units (atm, kPa, mmHg).

For Solutions with multiple ions, use the appropriate Van’t Hoff Factor to account for solute dissociation.

How to Calculate Osmotic Pressure?

To calculate Osmotic Pressure, apply Van’t Hoff’s Law, which relates pressure to concentration and temperature. Multiply the Molar Concentration by the Gas Constant, Absolute Temperature, and Van’t Hoff Factor.

The Van’t Hoff Factor accounts for solute dissociation in solution – for example, NaCl has a factor of 2, while CaCl₂ has a factor of 3. Convert temperature to Kelvin if needed by adding 273.15 to Celsius values.

Formula for Osmotic Pressure Calculation

Basic Osmotic Pressure Formula:

π = MiRT
where:
π = Osmotic Pressure (atm)
M = Molar Concentration (mol/L)
i = Van't Hoff Factor
R = Gas Constant (0.08206 L⋅atm⋅mol⁻¹⋅K⁻¹)
T = Temperature (K)

Temperature Conversion:

T(K) = T(°C) + 273.15
where:
T(K) = Temperature in Kelvin
T(°C) = Temperature in Celsius

Pressure Unit Conversions:

1 atm = 101.325 kPa
1 atm = 760 mmHg

Example 1

• Glucose C = 0.1 mol/L, i = 1, T = 25 + 273.15 = 298.15 K π = 1 0.1 0.0821 * 298.15 = 2.447 atm

Example 2

• NaCl C = 0.2 mol/L, i = 2, T = 30 + 273.15 = 303.15 K π = 2 0.2 0.0821 * 303.15 = 9.938 atm

Example 3

• MgCl_2 C = 0.05 mol/L, i = 3, T = 20 + 273.15 = 293.15 K π = 3 0.05 0.0821 * 293.15 = 3.606 atm

Example 4

• Sucrose C = 0.15 mol/L, i = 1, T = 40 + 273.15 = 313.15 K π = 1 0.15 0.0821 * 313.15 = 3.857 atm

Example 5

• KCl C = 0.3 mol/L, i = 2, T = 10 + 273.15 = 283.15 K π = 2 0.3 0.0821 * 283.15 = 13.912 atm

What is Osmotic Pressure?

Osmotic Pressure is the minimum pressure required to prevent the flow of solvent across a Semipermeable Membrane into a solution. It’s a Colligative Property that depends on the number of dissolved particles rather than their identity. The Van’t Hoff Factor accounts for Solute Dissociation in solution, making the actual osmotic pressure higher for Electrolytes compared to Non-electrolytes at the same concentration.