When `CuSO_4` is added to a solution of ammonia

Options

A. Freezing point is lowered
B. Freezing point is raised
C. Boiling point is raised
D. Both (1) & (3)

Answer

To solve the question "When `CuSO4` is added to a solution of ammonia," we need to analyze the effects of adding `CuSO4` on the freezing point and boiling point of the ammonia solution.

### Step-by-Step Solution:

1. **Understanding the Components**:
- We have a solution of ammonia (NH₃) and we are adding copper(II) sulfate (CuSO₄) to it.
- CuSO₄ is a salt that will dissociate in solution into its ions: Cu²⁺ and SO₄²⁻.

2. **Effect on Freezing Point**:
- The freezing point depression can be calculated using the formula:
\[ \Delta T_f = i \cdot K_f \cdot m \]
where:
- \( \Delta T_f \) = depression in freezing point,
- \( i \) = van 't Hoff factor (number of particles the solute dissociates into),
- \( K_f \) = freezing point depression constant of the solvent (ammonia in this case),
- \( m \) = molality of the solution.

3. **Calculating the Van 't Hoff Factor (i)**:
- For CuSO₄, it dissociates into 3 particles: Cu²⁺ and SO₄²⁻. Thus, \( i = 3 \).

4. **Effect on Molality (m)**:
- When CuSO₄ is added to the ammonia solution, the molality of the solution increases because we are adding more solute.

5. **Conclusion on Freezing Point**:
- Since both \( i \) and \( m \) increase, \( \Delta T_f \) will increase, leading to a lower freezing point of the solution.
- Therefore, the freezing point is lowered.

6. **Effect on Boiling Point**:
- The boiling point elevation can be calculated using the formula:
\[ \Delta T_b = i \cdot K_b \cdot m \]
where:
- \( \Delta T_b \) = elevation in boiling point,
- \( K_b \) = boiling point elevation constant of the solvent.

7. **Conclusion on Boiling Point**:
- Similar to freezing point, since \( i \) and \( m \) increase, \( \Delta T_b \) will also increase, leading to a higher boiling point of the solution.
- Therefore, the boiling point is raised.

8. **Final Answer**:
- The correct options are:
- Freezing point is lowered (1)
- Boiling point is raised (3)
- Thus, the answer is both 1 and 3.