# Colligative Properties Calculator

Free colligative properties calculator. Calculate boiling point elevation, freezing point depression for solutions with multiple solvent options.

## What this calculates

Calculate boiling point elevation (ΔT_b = i·K_b·m) and freezing point depression (ΔT_f = i·K_f·m) for solutions. Supports water, benzene, cyclohexane, camphor, and custom solvents.

## Inputs

- **Property to Calculate** — options: Boiling Point Elevation (ΔT_b), Freezing Point Depression (ΔT_f), Both (from molality) — Select which colligative property to calculate.
- **Molality (m)** (mol/kg) — min 0 — Molality of the solution (moles solute / kg solvent).
- **van't Hoff Factor (i)** — min 1, max 10 — Number of particles: non-electrolyte=1, NaCl=2, CaCl₂=3.
- **Solvent** — options: Water (K_b=0.512, K_f=1.86), Benzene (K_b=2.53, K_f=5.12), Acetic Acid (K_b=3.07, K_f=3.90), Cyclohexane (K_b=2.79, K_f=20.0), Camphor (K_b=5.95, K_f=37.7), Custom (enter K values below) — Select solvent for K_b and K_f constants.
- **K_b (Ebullioscopic Constant)** (°C·kg/mol) — min 0 — Boiling point elevation constant for custom solvent.
- **K_f (Cryoscopic Constant)** (°C·kg/mol) — min 0 — Freezing point depression constant for custom solvent.
- **Normal Boiling Point** (°C) — Normal boiling point of the pure solvent.
- **Normal Freezing Point** (°C) — Normal freezing point of the pure solvent.

## Outputs

- **Boiling Point Elevation (ΔT_b)** (°C) — How much the boiling point is raised.
- **New Boiling Point** (°C) — Boiling point of the solution.
- **Freezing Point Depression (ΔT_f)** (°C) — How much the freezing point is lowered.
- **New Freezing Point** (°C) — Freezing point of the solution.
- **Formulas** — formatted as text — Step-by-step calculations.

## Frequently Asked Questions

**Q: What are colligative properties?**

A: Colligative properties depend only on the number of solute particles, not their identity. They include boiling point elevation, freezing point depression, vapor pressure lowering, and osmotic pressure.

**Q: Why does salt lower the freezing point of water?**

A: Salt (NaCl) dissociates into Na⁺ and Cl⁻ ions, disrupting the crystal lattice formation needed for freezing. The freezing point drops proportionally to the number of dissolved particles: ΔT_f = i·K_f·m.

**Q: What is the van't Hoff factor?**

A: The van't Hoff factor (i) represents how many particles a solute produces when dissolved. Non-electrolytes like glucose have i=1. Electrolytes dissociate: NaCl gives i=2, CaCl₂ gives i=3.

**Q: Why does camphor have such a large K_f?**

A: Camphor's large K_f (37.7°C·kg/mol) makes it very sensitive to solute concentration, which is why it has historically been used in molecular weight determination by freezing point depression (Rast method).

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Source: https://vastcalc.com/calculators/chemistry/colligative-properties
Category: Chemistry
Last updated: 2026-04-21