Question

State Raoult's law for a solution containing volatile components. Write any two characteristics of a solution which obeys Raoult's law at all concentrations.

Hint:

Ideal solutions perfectly obey Raoult's law without any volume or enthalpy change upon mixing.

Answer 1

Step 1: Concept
Raoult's law defines the fundamental relationship between the vapour pressure of a solution and the mole fraction of its volatile components.

Step 2: Meaning
It states that the partial vapour pressure of each component is directly proportional to its mole fraction in the solution.

Step 3: Analysis
Solutions that perfectly obey this law at all concentrations and temperatures are classified as ideal solutions. For such solutions, the intermolecular forces between the mixed components (A-B) are exactly the same as those in the pure components (A-A and B-B). This results in an enthalpy of mixing ($\Delta H_{mix}$) of zero and a volume of mixing ($\Delta V_{mix}$) of zero.

Final Answer: Raoult's law states that for a solution of volatile liquids, the partial vapour pressure of each component in the solution is directly proportional to its mole fraction. Two characteristics of a solution that perfectly obeys Raoult's law (an ideal solution) are: 1. $\Delta H_{mix} = 0$ (no heat is absorbed or evolved). 2. $\Delta V_{mix} = 0$ (the total volume equals the sum of the individual volumes).