Question

Which of the following statements is correct regarding a solution of two components A and B exhibiting positive deviation from ideal behaviour?

Options

• Intermolecular attractive forces between A-A and B-B are equal to those between A-B.

• Intermolecular attractive forces between A-A and B-B are stronger than those between A-B.

• Δ_mix H = 0 at constant T and P.

• Δ_mix V = 0 at constant T and P.

Answer 1

Intermolecular attractive forces between A-A and B-B are stronger than those between A-B.

Explanation:

A positive deviation from Raoult’s law occurs when the A-B interactions are weaker than the A-A and B-B interactions. This weaker interaction causes the solution to have higher vapour pressure than expected since molecules escape more easily.