Colligative Properties Calculator

Colligative properties are physical properties of solutions that depend only on the concentration of solute particles, not their identity. The main colligative properties are boiling point elevation, freezing point depression, osmotic pressure, and vapor pressure lowering.

The van't Hoff factor (i) represents the number of particles a solute dissociates into when dissolved. For non-electrolytes like sugar, i = 1. For NaCl, i ≈ 2 (Na⁺ + Cl⁻). For CaCl₂, i ≈ 3 (Ca²⁺ + 2Cl⁻). The actual value may be slightly less due to ion pairing.

Boiling point elevation is calculated using ΔTb = i × Kb × m, where i is the van't Hoff factor, Kb is the ebullioscopic constant of the solvent, and m is the molality of the solution. The new boiling point is the normal boiling point plus ΔTb.

Molality (m) is moles of solute per kilogram of solvent, while molarity (M) is moles of solute per liter of solution. Molality is used for colligative properties because it doesn't change with temperature, unlike molarity.

For water, the ebullioscopic constant (Kb) is 0.512 °C·kg/mol and the cryoscopic constant (Kf) is 1.86 °C·kg/mol. These constants are specific to each solvent and are used in colligative property calculations.

Freezing point depression is calculated using ΔTf = i × Kf × m. The new freezing point is the normal freezing point minus ΔTf. This is why salt is used to melt ice on roads - it lowers the freezing point of water.

Use simple mode when you already know the molality of your solution. Use advanced mode when you need to calculate molality from the masses of solute and solvent. Advanced mode automatically calculates molality using: m = (mass of solute / molar mass) / (mass of solvent in kg).

Osmotic pressure is the pressure required to prevent the flow of solvent through a semipermeable membrane. It's calculated using π = i × M × R × T, where M is molarity, R is the gas constant (0.0821 L·atm/mol·K), and T is absolute temperature in Kelvin.