Answer: Decreases.
- A Increases
- B Decreases
- C Remains the same
- D Becomes zero
Correct answer: B. Decreases
Explanation: Adding solute reduces solvent molecules at the surface (Raoult's law), lowering vapour pressure.
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.