Question 1

What are colligative properties?

Accepted Answer

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.

Question 2

Why does salt lower the freezing point of water?

Accepted Answer

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.

Question 3

What is the van't Hoff factor?

Accepted Answer

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.

Question 4

Why does camphor have such a large K_f?

Accepted Answer

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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