At ${35}^{\mathrm{o}}\mathrm{C}$ the vapour pressure of $\mathrm{C}{\mathrm{S}}_2$ is 512 mm Hg, and of acetone, $\mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{C}{\mathrm{H}}_3$ , is 344 mm Hg. A solution of $\mathrm{C}{\mathrm{S}}_2$ and acetone in which the mole fraction of $\mathrm{C}{\mathrm{S}}_2$ is 0.25 has a total vapour pressure of 600 mm Hg. Which of the following statements about solution of acetone - $\mathrm{C}{\mathrm{S}}_2$ is true ?

• A

  A mixture of 100 ml of acetone and 100 ml of $\mathrm{C}{\mathrm{S}}_2$ has a total volume of 200 ml.
• Correct answer
  B

  When acetone and $\mathrm{C}{\mathrm{S}}_2$ are mixed at ${35}^{\mathrm{o}}\mathrm{C}$ , heat must be absorbed in order to produce a solution at ${35}^{\mathrm{o}}\mathrm{C}$ .
• C

  When acetone and $\mathrm{C}{\mathrm{S}}_2$ are mixed at ${35}^{\mathrm{o}}\mathrm{C}$ , heat is released.
• D

  Raoult's law is obeyed by both $\mathrm{C}{\mathrm{S}}_2$ and acetone for the solution in which the mole fraction of $\mathrm{C}{\mathrm{S}}_2$ is 0.25.

Hence, the correct answer is option: 'B'.