Out of ` Ca^(2+) ,Al^(3+) , Bi^(3+) ,Mg^(2+) and Zn^(2+) ` the reagents `NH_4Cl ` and aqueous `NH_3` will precipitate

Options

A. `Ca^(2+) , Al^(3+)`
B. `Al^(3+) , Bi^(3+)`
C. `Bi^(3+) , Mg^(2+)`
D. `Mg^(2+), Zn^(2+)`

Answer

To determine which ions among \( \text{Ca}^{2+}, \text{Al}^{3+}, \text{Bi}^{3+}, \text{Mg}^{2+}, \text{Zn}^{2+} \) will precipitate when reacted with \( \text{NH}_4\text{Cl} \) and aqueous \( \text{NH}_3 \), we can follow these steps:

### Step 1: Understand the Reaction
When \( \text{NH}_4\text{Cl} \) and \( \text{NH}_3 \) are added to a solution containing metal ions, they can form insoluble hydroxides or chlorides. The key is to identify which metal ions form precipitates under these conditions.

### Step 2: Identify the Relevant Metal Ions
The metal ions given are:
- \( \text{Ca}^{2+} \) (Calcium)
- \( \text{Al}^{3+} \) (Aluminium)
- \( \text{Bi}^{3+} \) (Bismuth)
- \( \text{Mg}^{2+} \) (Magnesium)
- \( \text{Zn}^{2+} \) (Zinc)

### Step 3: Consider Solubility Products
The solubility product (Ksp) is a key factor in determining whether a precipitate will form. Generally, ions with lower solubility products will precipitate first.

- **Aluminium Hydroxide** (\( \text{Al(OH)}_3 \)): Low solubility
- **Bismuth Hydroxide** (\( \text{Bi(OH)}_3 \)): Low solubility
- **Calcium Hydroxide** (\( \text{Ca(OH)}_2 \)): Moderate solubility
- **Magnesium Hydroxide** (\( \text{Mg(OH)}_2 \)): Low solubility
- **Zinc Hydroxide** (\( \text{Zn(OH)}_2 \)): Low solubility

### Step 4: Identify Precipitating Ions
From the above analysis:
- \( \text{Al}^{3+} \) and \( \text{Bi}^{3+} \) will precipitate as their hydroxides when reacted with \( \text{NH}_4\text{Cl} \) and \( \text{NH}_3 \).
- \( \text{Mg}^{2+} \) and \( \text{Zn}^{2+} \) can also precipitate, but the question specifically asks for the ions that will precipitate under the influence of \( \text{NH}_4\text{Cl} \) and \( \text{NH}_3 \).

### Step 5: Conclusion
The ions that will precipitate are \( \text{Al}^{3+} \) and \( \text{Bi}^{3+} \). Therefore, the correct answer is:

**Option 2: Aluminium and Bismuth.**

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