Question

Choose the correct statements regarding liquid - liquid solutions having stronger solvent-solvent interactions than solvent-solute interactions.

• A. The system is exothermic.
• B. Vapour pressure of the resultant solution is higher.
• C. Shows positive deviation from Raoult's law
• D. Can form minimum boiling azeotropes.

Answer 1

Answer: (B), (C), (D)

Can form minimum boiling azeotropes.

In case of positive deviation from Raoult’s law, A-B interactions are weaker than those between A-A or B-B interactions. In this case, the intermolecular attractive forces between the solute-solvent molecules are weaker than those between the solute-solute and solvent-solvent molecules. This means that in such solutions, molecules of A (or B) will find it easier to escape than in pure state. This will increase the vapour pressure and result in positive deviation.
The solutions which show a large positive deviation from Raoult’s law form minimum boiling azeotrope at a specific composition.
A mixture of phenol and aniline is an example for solutions showing negative deviation from Raoult's law.