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

Explanation

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

### Step-by-Step Solution:

1. **Understand the Concept of Positive Deviation from Raoult's Law**:
- A positive deviation from Raoult's law occurs when the vapor pressure of the solution is greater than what would be expected based on the vapor pressures of the pure components. This typically happens when the interactions between different molecules in the solution are weaker than the interactions between molecules of the same kind.

2. **Identify the Boiling Points**:
- The normal boiling point of pure acetone is lower than that of pure carbon disulfide (CS₂). This means that when mixed, the solution will have a boiling point that is influenced by the properties of both components.

3. **Analyze the Statements**:
- Since the question does not provide specific statements, we will assume typical statements that might be made regarding this scenario:
- Statement A: The boiling point of the acetone-CS₂ solution will be higher than that of pure acetone.
- Statement B: The vapor pressure of the solution will be less than that of pure acetone.
- Statement C: The solution will exhibit a boiling point lower than that of pure CS₂.
- Statement D: The solution will show a positive deviation from Raoult's law.

4. **Evaluate Each Statement**:
- **Statement A**: True. The boiling point of the solution will be higher than that of pure acetone due to the positive deviation.
- **Statement B**: False. The vapor pressure of the solution will be greater than that of pure acetone because of the positive deviation.
- **Statement C**: False. The boiling point of the solution will not be lower than that of pure CS₂; it will be higher than that of acetone but can be lower or higher than CS₂ depending on the composition.
- **Statement D**: True. The solution indeed shows a positive deviation from Raoult's law.

5. **Conclusion**:
- The incorrect statement among the assumed options is **Statement B**: "The vapor pressure of the solution will be less than that of pure acetone." This statement is false because the solution exhibits a positive deviation, meaning its vapor pressure is higher.

### Final Answer:
The incorrect statement is: "The vapor pressure of the solution will be less than that of pure acetone."