Name the reagent from the following which can be used to distinguish zinc nitrate solution from magnesium nitrate.

Options

A. `NH_(4)OH` (aq)
B. `NaOH` (aq)
C. `BaCl_(2)`
D. `H_(2)SO_(4)`

Explanation

To distinguish between zinc nitrate (Zn(NO3)2) and magnesium nitrate (Mg(NO3)2), we can use ammonium hydroxide (NH4OH) or sodium hydroxide (NaOH) as reagents. Here’s a step-by-step explanation of how these reagents can be used:

### Step 1: Reaction with Ammonium Hydroxide (NH4OH)
1. **Zinc Nitrate Reaction**:
- When zinc nitrate is treated with ammonium hydroxide, it forms zinc hydroxide (Zn(OH)2) as a precipitate:
\[ \text{Zn(NO}_3\text{)}_2 + 2 \text{NH}_4\text{OH} \rightarrow \text{Zn(OH)}_2 \downarrow + 2 \text{NH}_4\text{NO}_3 \]
- The zinc hydroxide can further react with excess ammonium hydroxide to form a soluble complex:
\[ \text{Zn(OH)}_2 + 4 \text{NH}_4\text{OH} \rightarrow \text{[Zn(NH}_3\text{)}_4]^{2+} + 2 \text{H}_2\text{O} \]

2. **Magnesium Nitrate Reaction**:
- When magnesium nitrate is treated with ammonium hydroxide, it also forms magnesium hydroxide (Mg(OH)2) as a precipitate:
\[ \text{Mg(NO}_3\text{)}_2 + 2 \text{NH}_4\text{OH} \rightarrow \text{Mg(OH)}_2 \downarrow + 2 \text{NH}_4\text{NO}_3 \]
- However, magnesium hydroxide does not react further with excess ammonium hydroxide.

### Step 2: Reaction with Sodium Hydroxide (NaOH)
1. **Zinc Nitrate Reaction**:
- When zinc nitrate is treated with sodium hydroxide, it forms zinc hydroxide (Zn(OH)2) as a precipitate:
\[ \text{Zn(NO}_3\text{)}_2 + 2 \text{NaOH} \rightarrow \text{Zn(OH)}_2 \downarrow + 2 \text{NaNO}_3 \]
- Similar to the ammonium hydroxide reaction, zinc hydroxide can react with excess sodium hydroxide to form sodium zincate:
\[ \text{Zn(OH)}_2 + 2 \text{NaOH} \rightarrow \text{Na}_2\text{Zn(OH)}_4 + 2 \text{H}_2\text{O} \]

2. **Magnesium Nitrate Reaction**:
- When magnesium nitrate is treated with sodium hydroxide, it forms magnesium hydroxide (Mg(OH)2) as a precipitate:
\[ \text{Mg(NO}_3\text{)}_2 + 2 \text{NaOH} \rightarrow \text{Mg(OH)}_2 \downarrow + 2 \text{NaNO}_3 \]
- Magnesium hydroxide does not react further with excess sodium hydroxide.

### Conclusion:
- **Distinguishing Factor**: The key difference is that zinc hydroxide can react further with excess NH4OH or NaOH to form soluble complexes or salts, while magnesium hydroxide does not undergo further reaction. Therefore, using either ammonium hydroxide or sodium hydroxide allows us to distinguish between zinc nitrate and magnesium nitrate.

### Final Answer:
The reagents that can be used to distinguish zinc nitrate from magnesium nitrate are **Ammonium Hydroxide (NH4OH)** and **Sodium Hydroxide (NaOH)**.

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