Answer: Acetic acid molecules associate (dimerise) in benzene, reducing the effective number of particles in solution.
- A Acetic acid molecules associate (dimerise) in benzene, reducing the effective number of particles in solution
- B Benzene reacts chemically with acetic acid to form a new, more concentrated solute under normal conditions
- C The molar mass of acetic acid effectively rises when dissolved in benzene due to solvation as generally observed
- D Acetic acid dissociates into ions more readily when dissolved in benzene than in water in typical laboratory settings
Correct answer: A. Acetic acid molecules associate (dimerise) in benzene, reducing the effective number of particles in solution
Explanation: In a non-polar solvent like benzene, acetic acid molecules associate through hydrogen bonding to form dimers, decreasing the number of effective particles and giving i less than 1.
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.