What happens when ammonia solution is added first drop-wise and then in excess to zinc sulphate?

Options

A. A reddish brown ppt is formed which is insoluble in excess of alkali.
B. Dirty green ppt is formed which is insoluble in excess of alkali.
C. A gelatinous white ppt is formed which is soluble in excess of alkali.
D. No ppt will be formed even in excess of alkali.

Explanation

### Step-by-Step Text Solution

1. **Identify the Reactants**:
- The reactants in this scenario are ammonia solution (which can be represented as ammonium hydroxide, NH₄OH) and zinc sulfate (ZnSO₄).

2. **First Step - Adding Ammonia Drop-wise**:
- When ammonia solution is added drop-wise to zinc sulfate, a reaction occurs where zinc sulfate reacts with ammonium hydroxide.
- The reaction can be represented as:
\[ ZnSO_4 + 2NH_4OH \rightarrow Zn(OH)_2 + (NH_4)_2SO_4 \]
- Here, zinc hydroxide (Zn(OH)₂) is formed as a white gelatinous precipitate along with ammonium sulfate \((NH_4)_2SO_4\).

3. **Observation**:
- The first observable result is the formation of a white gelatinous precipitate of zinc hydroxide when ammonia is added drop-wise.

4. **Second Step - Adding Ammonia in Excess**:
- When excess ammonia solution is added to the mixture containing the precipitate, the zinc hydroxide precipitate dissolves.
- The reaction can be represented as:
\[ Zn(OH)_2 + 4NH_4OH \rightarrow [Zn(NH_4)_4](SO_4) + 4H_2O \]
- This results in the formation of a soluble complex, tetraamminezinc(II) sulfate \([Zn(NH_4)_4](SO_4)\), and water.

5. **Final Observation**:
- The final observation is that the white precipitate dissolves in excess ammonia, resulting in a colorless solution.

### Summary of the Reactions:
- **First Reaction**: Formation of a white gelatinous precipitate (Zn(OH)₂).
- **Second Reaction**: Dissolution of the precipitate in excess ammonia, forming a colorless solution of a zinc complex.

### Conclusion:
- When ammonia solution is added drop-wise to zinc sulfate, a white gelatinous precipitate forms. When excess ammonia is added, this precipitate dissolves to form a colorless solution.

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