Osmotic Pressure Calculator

The Osmotic Pressure Calculator computes the pressure required to stop osmosis across a semi-permeable membrane. Osmotic pressure depends on solute concentration, temperature, dissociation factor, and the osmotic coefficient.

$$\pi = n \cdot \Phi \cdot c \cdot R \cdot T$$

where $\pi$ is osmotic pressure (Pa), $n$ is the number of ions produced when the solute dissociates (van't Hoff factor), $\Phi$ is the osmotic coefficient, $c$ is molar concentration (mol/L), $R$ is the gas constant (8.314 J/(K·mol)), and $T$ is temperature in Kelvin.

Example: 1 g of Na₂SO₄ ($M = 142$ g/mol, $n = 3$, $\Phi = 0.74$) in 0.1 L at 30 °C gives $c = 0.07042$ mol/L and $\pi = 3940.6$ hPa.

Osmotic pressure is used in water purification, desalination, reverse osmosis design, and biological systems such as cell membrane studies.

Frequently Asked Questions

What is osmotic pressure?

Osmotic pressure is the minimum pressure needed to prevent solvent flow through a semi-permeable membrane. It measures how strongly a solution draws solvent across the membrane.

What is the van't Hoff factor?

The van't Hoff factor ($n$) is the number of particles a solute produces when dissolved. NaCl gives 2 ions ($n = 2$), while glucose does not dissociate ($n = 1$).

What is the osmotic coefficient?

The osmotic coefficient ($\Phi$) corrects for non-ideal behavior in real solutions. It is usually close to 1 for ideal solutions and lower for electrolytes at higher concentrations.

How do I calculate concentration from mass?

Divide the mass of solute in grams by the product of molar mass and solution volume: $c = m / (M \times V)$. This calculator can compute concentration automatically from mass, molar mass, and volume.

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Osmotic Pressure Calculator

Osmotic Pressure Calculator

Frequently Asked Questions

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