Identify the solution which is nearly ideal in behaviour
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Bromoethane and Chloroethane
A solution is nearly ideal when the A–B attractions are almost equal to the A–A and B–B attractions, so that ΔmixH ≈ 0 and ΔmixV ≈ 0 and Raoult’s law is obeyed. Bromoethane and chloroethane are very similar molecules with similar intermolecular forces, so their solution is nearly ideal.
Why the other options are incorrect
Option (1) Ethanol and Acetone — Incorrect. Acetone breaks the hydrogen bonds of ethanol, so A–B attractions are weaker and the solution shows positive deviation.
Option (2) Phenol and Aniline — Incorrect. Hydrogen bonding between phenol and aniline makes A–B attractions stronger; the solution shows negative deviation.
Option (4) Chloroform and Acetone — Incorrect. Chloroform forms a hydrogen bond with the oxygen of acetone, giving negative deviation.
NCERT (2026-27 edition):
Ideal Solutions – …
