State Raoult's law for solutions of volatile liquid components. Taking a suitable example, explain the meaning of positive deviation from Raoult's law.
Solution
Raoult's law: for a solution of volatile liquids, the partial vapour pressure of each component is directly proportional to its mole fraction,
Positive deviation: the observed partial and total vapour pressures are higher than those calculated from Raoult's law. It arises when the A–B attractions are weaker than the A–A and B–B attractions.
Example: ethanol + acetone — acetone molecules break the hydrogen bonds between ethanol molecules, so both components escape more readily.
Positive deviation: the observed partial and total vapour pressures are higher than those calculated from Raoult's law. It arises when the A–B attractions are weaker than the A–A and B–B attractions.
Example: ethanol + acetone — acetone molecules break the hydrogen bonds between ethanol molecules, so both components escape more readily.
CBSE Class 12 Board · 2008 · All India · Subjective