Which among the following shows positive deviation from Raoult's law?

Ethanol and Acetone

The correct answer is Option (1) → Ethanol and Acetone
Positive deviation from Raoult’s law occurs when the intermolecular forces between unlike molecules (A–B) are weaker than those between like molecules (A–A and B–B). This makes molecules escape more easily into the vapour phase, increasing vapour pressure.

• • Ethanol + Acetone:
    Ethanol molecules are strongly hydrogen-bonded to each other. When acetone is mixed with ethanol, these hydrogen bonds are disrupted and the new interactions are weaker. Therefore, the mixture shows positive deviation.

  • Bromoethane + Chloroethane:
    Similar molecular sizes and similar intermolecular forces → behaves nearly ideally.

  • n-Hexane + n-Heptane:
    Both are non-polar hydrocarbons with similar dispersion forces → nearly ideal solution.

  • Chloroform + Acetone:
    Strong hydrogen bonding forms between them → negative deviation, not positive.

   Hence, Ethanol and Acetone shows positive deviation from Raoult’s law.