Binary liquid mixtures which exhibit positive deviations from Raoult’s law boil at ..... temperature than the expected b.pt -

Options

A. Lower
B. Higher
C. Same
D. Can't be said

Answer

To solve the question regarding binary liquid mixtures that exhibit positive deviations from Raoult’s law and their boiling point behavior, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Raoult's Law**:
- Raoult's law states that the vapor pressure of a component in a mixture is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture.
- For binary mixtures, if the interactions between different molecules (A and B) are weaker than those between like molecules (A with A and B with B), the mixture exhibits positive deviation.

**Hint**: Recall the definition of Raoult's law and the conditions for positive and negative deviations.

2. **Identifying Positive Deviation**:
- In a mixture showing positive deviation, the vapor pressure of the mixture is higher than expected based on Raoult's law. This occurs because the interactions between A and B are weaker than the interactions between A-A and B-B.

**Hint**: Remember that positive deviation indicates weaker interactions between mixed components.

3. **Effect on Boiling Point**:
- The boiling point of a liquid is the temperature at which its vapor pressure equals the external atmospheric pressure.
- Since the vapor pressure of a mixture exhibiting positive deviation is higher, it will reach the atmospheric pressure at a lower temperature compared to what would be expected if the mixture followed Raoult's law perfectly.

**Hint**: Think about how vapor pressure relates to boiling point and how increased vapor pressure affects the boiling point.

4. **Conclusion**:
- Therefore, a binary liquid mixture that exhibits positive deviations from Raoult’s law will boil at a **lower temperature** than the expected boiling point.

**Hint**: Consider the relationship between vapor pressure and boiling point to finalize your answer.

### Final Answer:
The binary liquid mixtures which exhibit positive deviations from Raoult’s law boil at **lower temperature** than the expected boiling point.