What is meant by positive deviation from Raoul's Law ? Give an example. What is the sign of `DeltaH_(mix)` for positive deviation ?

Explanation

### Step-by-Step Solution:

1. **Definition of Positive Deviation from Raoult's Law**:
- Positive deviation from Raoult's Law occurs when the observed vapor pressure of a mixture of two volatile liquids is greater than the vapor pressure predicted by Raoult's Law. This indicates that the interactions between the molecules of the different components in the mixture are weaker than the interactions between the molecules in the pure components.

2. **Explanation of Weaker Interactions**:
- In a mixture of two liquids, say A and B, the attractive forces between A and B are weaker compared to the attractive forces in pure A (A-A) or pure B (B-B). This weaker attraction allows more molecules to escape into the vapor phase, resulting in a higher vapor pressure than expected.

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