Acetone and carbon disulphide form binary liquid solution showing positive deviation from Raoult's law. The normal boiling point `(T_(b))` of pure acetone is less than that of pure `CS_(2)`. Pick out the incorrect statement among the following :

Options

A. Boiling temperature of mixture is always less than boiling temperature of acetone.
B. Boiling temperature of Azeotropic mixture is always less than boiling temperature of pure `CS_(2)`
C. When a small amount of `CS_(2)` (less volatile comoponent) is added to excess of aceton boiling point of resulting mixture increases.
D. A mixture of `CS_(2)` and `CH_(3)COCH_(3)` can be completely separated by simple fractional distillation.

Answer

To solve the question regarding the binary liquid solution of acetone and carbon disulfide (CS₂) that shows positive deviation from Raoult's law, we need to analyze the statements provided and identify the incorrect one.

### Step-by-Step Solution:

1. **Understanding Positive Deviation from Raoult's Law**:
- In a binary liquid solution, positive deviation from Raoult's law occurs when the interactions between the different components (solute-solvent) are weaker than the interactions between the like components (solute-solute and solvent-solvent). This leads to an increase in vapor pressure and a decrease in boiling point.

2. **Boiling Points of Pure Components**:
- The normal boiling point of pure acetone is less than that of pure carbon disulfide (CS₂). This means that acetone has a lower boiling point compared to CS₂.

3. **Behavior of the Mixture**:
- Due to positive deviation, the boiling point of the mixture will be lower than that of the higher boiling component (CS₂). Therefore, the boiling point of the mixture will be less than that of pure CS₂.

4. **Azeotropic Behavior**:
- Since the solution shows positive deviation, it is likely to form a minimum boiling point azeotrope. This means that the mixture will boil at a constant temperature, which is lower than the boiling points of both pure components.

5. **Analyzing the Statements**:
- **Statement 1**: "The boiling point of the mixture is always less than the boiling point of acetone."
- This statement is incorrect because the boiling point of the mixture will be less than that of CS₂ but not necessarily less than that of acetone.
- **Statement 2**: "When a small amount of CS₂ is added to excess acetone, the boiling point of the resulting mixture increases."
- This statement is correct as adding CS₂ to acetone will initially increase the boiling point until the azeotropic point is reached.
- **Statement 3**: "The mixture of CS₂ and acetone can be completely separated by simple fractional distillation."
- This statement is incorrect because the presence of an azeotropic mixture means that they cannot be completely separated by fractional distillation.
- **Statement 4**: "The boiling point of the azeotropic mixture will be less than the boiling point of pure CS₂."
- This statement is correct since the azeotropic mixture has a lower boiling point than that of CS₂.

6. **Conclusion**:
- The incorrect statements are 1 and 3. Therefore, the answer to the question is that the incorrect statements among the options provided are Statement 1 and Statement 3.

### Summary of Incorrect Statements:
- **Statement 1**: Incorrect (The boiling point of the mixture is not always less than that of acetone).
- **Statement 3**: Incorrect (The mixture cannot be completely separated by fractional distillation due to azeotropic behavior).