Which of the following solutions will have the maximum lowering of vapour pressure

Options

A. `1M - CaCl_(2)`
B. `1M - NaCl`
C. 1N - Phenol
D. 1M - Sucrose

Answer

To determine which solution will have the maximum lowering of vapor pressure, we need to consider the van 't Hoff factor (i) for each solute. The lowering of vapor pressure is directly related to the number of particles (ions or molecules) in solution, which is represented by the van 't Hoff factor.

### Step-by-Step Solution:

1. **Identify the Solutes**: We need to analyze the solutes provided in the question. Let's assume the solutes are:
- CaCl2
- NaCl
- Phenol
- Sucrose

2. **Determine the van 't Hoff Factor (i)**:
- **For CaCl2**: When CaCl2 dissolves in water, it dissociates into 1 Ca²⁺ ion and 2 Cl⁻ ions. Therefore, the total number of particles is 3.
- \( i = 3 \)
- **For NaCl**: When NaCl dissolves, it dissociates into 1 Na⁺ ion and 1 Cl⁻ ion. Thus, the total number of particles is 2.
- \( i = 2 \)
- **For Phenol**: Phenol can dissociate into phenoxide ions and hydrogen ions, but it does not dissociate completely like ionic compounds. For simplicity, we can consider it as producing 2 particles.
- \( i = 2 \)
- **For Sucrose**: Sucrose is a non-electrolyte and does not dissociate in solution. Therefore, it remains as one particle.
- \( i = 1 \)

3. **Compare the van 't Hoff Factors**:
- CaCl2: \( i = 3 \)
- NaCl: \( i = 2 \)
- Phenol: \( i = 2 \)
- Sucrose: \( i = 1 \)

4. **Determine the Maximum Lowering of Vapor Pressure**:
The lowering of vapor pressure is proportional to the van 't Hoff factor. The solution with the highest van 't Hoff factor will have the maximum lowering of vapor pressure.
- Since CaCl2 has the highest van 't Hoff factor of 3, it will cause the maximum lowering of vapor pressure.

### Conclusion:
The solution that will have the maximum lowering of vapor pressure is **CaCl2**.