Question

Which of the following is correct for a solution containing liquids A and B that show positive deviation from Raoult's law?

• A. Total vapour pressure is less than what it should be according to Raoult's Law.
• B. Total vapour pressure is more than what it should be according to Raoult's Law.
• C. Total vapour pressure is equal to what it should be according to Raoult's Law.
• D. Cannot be determined.

Answer 1

The correct option is B Total vapour pressure is more than what it should be according to Raoult's Law.

Liquids showing positive deviation will have total vapour pressure more than what it should be according to Raoult's Law because solvent-solute interaction is less than the solvent-solvent and the solute-solute interactions

$P_T>p_A^{\circ }{\chi }_A+p_B^{\circ }{\chi }_B$