Question

At 35$^{\circ}$C, the vapour pressure of $CS_2$ is 512 mm Hg and that of acetone is 344 mm Hg. A solution of $CS_2$, in acetone has a total vapour pressure of 600 mm Hg. The false statement amongst the following is :

• A. heat must be absorbed in order to produce the solution at 35$^{\circ}$C
• B. a mixture of 100 mL $CS_2$, and 100 mL acetone has a volume < 200 mL
• C. $CS_2$, and acetone are less attracted to each other than to themselves
• D. Raoult's law is not obeyed by this system

Answer 1

Answer: (B)

a mixture of 100 mL $CS_2$, and 100 mL acetone has a volume < 200 mL

Answer 2

The vapour pressure of mixture ( = 600 mm Hg) is greater than the individual vapour pressure of its constituents (Vapour pressure of $Cs_{2}=$ 512 mm Hg, acetone = 344 mm Hg). Hence, the solution formed shows positive deviation from Raoult's law.
$\Rightarrow\, \left(1\right)\Delta_{sol} H>\, 0, \left(2\right)$ Raoult's law is not obeyed
$\left(3\right) \Delta_{sol} . Volume \, >\, 0$
$\left(4\right)Cs_{2}$ and Acetone are less attracted to each ether than to themselves.