Question

Out of the following liquid pairs, the solution which shows a positive deviation from Raoult’s law is:

• A. Acetone + Chloroform
• B. Water + Nitric acid
• C. Water + Hydrochloric acid
• D. Benzene + Methanol

Answer 1

The correct option is D Benzene + Methanol

A mixture of non-ideal binary solution will show a negative deviation from Raoult's law when $A-B$ interaction is stronger than $A-A$ and $B-B$ interaction and vice versa

• In case of acetone and $CHC{l}_3$, there is a scope of H-bond formation which is stronger than dipole-dipole interaction, so the solution mixture shows a negative deviation
• In case of water + nitric acid and water + Hydrochloric acid, The $A-B$ type interaction is ion - dipole interaction which is stronger than H - bond so the solution mixture shows a negative deviation
• Now in case of benzene + methanol , The $A-B$ type interaction is dipole-induced dipole which is weaker than H-bond in methanol so the solution mixture shows a positive deviation