Answer: stronger than in pure liquids.
- A weaker than in the pure liquids
- B stronger than in pure liquids
- C more or less completely absent
- D identical to the ideal case
Correct answer: B. stronger than in pure liquids
Explanation: Stronger A–B attractions hold molecules back, lowering the vapour pressure below the ideal value.
Adding a non-volatile solute lowers the solvent's vapour pressure at every temperature, which is the root cause behind all four colligative properties: it shifts the freezing point down and the boiling point up.
Concept context
Learn how substances dissolve and form mixtures. Covers concentration terms, colligative properties (boiling point elevation, freezing point depression, osmotic pressure), and ideal vs non-ideal solution behaviour.