Question

20 mL of a liquid A was mixed with 20 mL of liquid B. The volume of resulting solution was found to be less than 40 mL. What do you conclude from the above data?

Answer 1

Step 1: When two liquids A and B are mixed, if the resulting volume is less than the sum of their individual volumes, it indicates that the intermolecular forces between A and B are stronger than those between A–A and B–B.
Step 2: This causes the molecules to come closer, leading to volume contraction.
Conclusion: The solution exhibits negative deviation from Raoult’s Law.

Answer 2

Step 1: Positive deviation from Raoult’s law occurs when A–B interactions are weaker than A–A and B–B interactions.
Step 2: This results in:
- Increased escaping tendency of molecules,
- Increased vapour pressure,
- Volume expansion.
Step 3: In the given options, Carbon disulphide and Acetone form a non-ideal solution with weak intermolecular forces, leading to positive deviation.

Answer 3

Step 1: According to Raoult’s law:

\[ P_{\text{solution}} = P^0_{\text{solvent}} \times X_{\text{solvent}} \]

Step 2: Let \( X_{\text{solute}} = x \), then:

\[ X_{\text{solvent}} = 1 - x \]

Step 3: Given:

\[ \begin{align*} P_{\text{solution}} &= 750 \, \text{mm Hg} \\ P^0_{\text{solvent}} &= 760 \, \text{mm Hg} \end{align*} \]

Step 4:

\[ \begin{align*} 750 &= 760(1 - x) \Rightarrow \frac{750}{760} = 1 - x \\ x &= 1 - \frac{750}{760} = \frac{10}{760} = 0.0132 \end{align*} \]

Conclusion: Mole fraction of glucose = 0.0132