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 will analyze the reaction and its effects on colligative properties step by step.

### Step 1: Write the Reaction
When copper(II) sulfate (`CuSO4`) is added to a solution of ammonia (`NH3`), a complex ion is formed. The reaction can be represented as follows:

\[ \text{CuSO}_4 (s) + 4 \text{NH}_3 (aq) \rightarrow [\text{Cu(NH}_3\text{)}_4]^{2+} (aq) + \text{SO}_4^{2-} (aq) \]

### Step 2: Analyze the Reactants and Products
In the reaction:
- On the reactant side, we have 1 molecule of `CuSO4` and 4 molecules of `NH3`, totaling 5 molecules.
- On the product side, we have 1 complex ion `[\text{Cu(NH}_3\text{)}_4]^{2+}` and 1 sulfate ion `\text{SO}_4^{2-}`, totaling 2 ions.

### Step 3: Count the Number of Ions
- Reactants: 5 molecules (1 `CuSO4` + 4 `NH3`)
- Products: 2 ions (`[\text{Cu(NH}_3\text{)}_4]^{2+}` and `\text{SO}_4^{2-}`)

### Step 4: Understand Colligative Properties
Colligative properties depend on the number of solute particles in a solution. The two main colligative properties we will consider are:
- Depression in freezing point
- Elevation in boiling point

### Step 5: Determine the Effect on Boiling Point and Freezing Point
- Since the number of particles decreases from 5 to 2, the effect on colligative properties will be as follows:
- **Boiling Point**: The boiling point of the solution will decrease because the number of ions is reduced.
- **Freezing Point**: The freezing point of the solution will increase because the number of ions is reduced.

### Conclusion
Based on the analysis:
- The correct conclusion is that the freezing point is raised, and the boiling point is lowered.

### Final Answer
The correct option is that the freezing point is raised, and the boiling point is lowered.

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