Calculate boiling point elevation (ΔTb) and freezing point depression (ΔTf) for ideal dilute solutions. Enter solute and solvent information to see how dissolved particles affect phase transition temperatures.
Enter solute and solvent information to calculate boiling point elevation (ΔTb) and freezing point depression (ΔTf) for ideal dilute solutions.
Colligative properties are physical properties of solutions that depend on the number of dissolved solute particles, not their chemical identity. When you dissolve a solute in a solvent, the solution behaves differently from the pure solvent in predictable ways.
The four main colligative properties are: vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure. This calculator focuses on boiling point elevation and freezing point depression, which are commonly used in chemistry education.
When a nonvolatile solute is dissolved in a solvent, the boiling point of the solution is higher than that of the pure solvent. This happens because solute particles reduce the vapor pressure of the solvent, requiring a higher temperature to reach the atmospheric pressure needed for boiling.
When a solute is dissolved in a solvent, the freezing point of the solution is lower than that of the pure solvent. Solute particles interfere with the formation of the orderly crystal lattice structure needed for freezing, requiring a lower temperature to solidify.
The van 't Hoff factor accounts for the fact that some solutes dissociate in solution, producing more particles than the original formula units. Since colligative properties depend on the number of particles, electrolytes have a larger effect than non-electrolytes.
| Solute Type | Example | Ideal i |
|---|---|---|
| Non-electrolyte | Glucose, Sucrose | 1 |
| Strong electrolyte (1:1) | NaCl, KBr | 2 |
| Strong electrolyte (1:2) | CaCl₂, MgBr₂ | 3 |
| Strong electrolyte (2:1) | Na₂SO₄ | 3 |
Note: In real solutions, the actual i value may be less than the ideal value due to ion pairing effects, especially at higher concentrations.
Colligative properties use molality (m) rather than molarity (M) because molality is temperature-independent:
Since molality is based on mass rather than volume, it doesn't change with temperature (unlike molarity, which changes as the solution expands or contracts).
Salt (NaCl or CaCl₂) is spread on icy roads to lower the freezing point of water, preventing ice formation or melting existing ice.
Sugar dissolved in water raises the boiling point, allowing candy makers to reach higher temperatures needed for different candy textures.
Ethylene glycol in car radiators lowers the freezing point while raising the boiling point, protecting the cooling system year-round.
By measuring freezing point depression, chemists can determine the molar mass of an unknown solute using solvents with large Kf values.
This calculator is designed for educational purposes to help students understand colligative properties. It assumes ideal dilute solution behavior and should not be used for designing real-world antifreeze formulations, pharmaceutical solutions, food products, or industrial processes. Real applications require professional engineering analysis that accounts for non-ideal behavior, safety factors, and regulatory requirements.
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