At `35^(@)C` the vapour pressure of `CS_‌(2)` is 512 mm Hg, and of acetone, `CH _(3) COCH _(3),` is 344 mm Hg. A solution of `CS_(2)` and acetone in which the mole fraction of `CS_(2)` is 0.25 has a total vapour pressure of 600 mm Hg. Which of the following statements about solution of acetone `CS_(2)` is true ?

Options

A. A mixture of 100 ml of acetone and 100 ml of `CS_(2)` has a total volume of 200 ml.
B. When acetone and `CS_(2)` are mixed at `35^(@)C,` heat must be absorbed in order to produce a solution at `35^(@)C.`
C. When acetone and `CS_(2)` are mixed at `35^(@)C,` heat is released.
D. Raoult's law is obeyed by both `CS_(2)` and acetone for the solution in which the mole fraction of `CS_(2)` is 0.25.

Answer

B

Explanation

`P _(T) = P _(A) ""^(@) X _(A) + P _(B) ""^(@) X _(B) = 512 xx 0. 25`
`+ ( 344 xx 0. 75)= 386` mm Hg.
`therefore` The solution is showing postive deviation
So For a solution of
Acetone `+ CS _(2) , Delta H = + ve`