Answer: Moles of solute per kg of solvent.
- A Moles of solute per litre of solution
- B Moles of solute per kg of solvent
- C Mass of solute per litre
- D Mole fraction of solute
Correct answer: B. Moles of solute per kg of solvent
Explanation: Molality (m) = moles of solute / mass of solvent in kg. It does not change with temperature.
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.