Question

At ${35}^{o}C$, the vapour pressure of $C{S}_{2}is512mmHg$ and that of acetone is $344mmHg$. A solution of $C{S}_2$ in acetone has a total vapour pressure of $600mmHg$. The false statement amongst the following is
(JEE MAIN 202)

• A. A mixture of 100 mL $C{S}_2$ and 100 mL acetone has a volume < 200 mL
• B. $C{S}_2$ and acetone are less attracted to each other than to themselves
• C. Raoult's law is not obeyed by this system
• D. Heat must be absorbed in order to produce the solution at $35°C$

Answer 1

The correct option is A A mixture of 100 mL $C{S}_2$ and 100 mL acetone has a volume < 200 mL

Since the vapour pressure of the solution is greater than individual vapour pressure of both pure components, the solution shows a positive deviation from Raoult's law.

Positive deviation: Solvent-solute interaction is less than the solvent-solvent and the solute-solute interactions.

Hence, the mixture of 100 mL $C{S}_2$ and 100 mL acetone has a volume greater than 200 mL.

For positive deviation: $\Delta H_{mix}>0$, Hence heat is absorbed during the mixing of $C{S}_2$ and acetone.
Hence, option (b) is correct answer.