The reagent `NH_4Cl` and aqueous `NH_(3)` will precipitate

Options

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

Explanation

To solve the question regarding the precipitation of ions when `NH4Cl` and aqueous `NH3` are mixed, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
The reactants in this scenario are ammonium chloride (`NH4Cl`) and aqueous ammonia (`NH3`).

2. **Understand the Role of the Reagents**:
`NH4Cl` is a source of ammonium ions (`NH4+`), and `NH3` in aqueous solution can act as a weak base, providing hydroxide ions (`OH-`). Together, they can precipitate certain metal ions.

3. **Determine the Group Reagents**:
The combination of `NH4Cl` and `NH4OH` (from `NH3` in water) serves as a group reagent for the third group of cations in qualitative analysis. This means they can precipitate certain metal ions.

4. **Identify the Precipitating Ions**:
The ions that can be precipitated by these reagents are primarily from the third group, which includes aluminum ions (`Al^3+`) and bismuth ions (`Bi^3+`).

5. **Evaluate the Given Options**:
- Option 1: Calcium (`Ca^2+`) - Not precipitated.
- Option 2: Aluminum (`Al^3+`) - Will precipitate.
- Option 3: Bismuth (`Bi^3+`) - Will precipitate.
- Option 4: Magnesium (`Mg^2+`) - Not precipitated.

6. **Conclusion**:
The correct answers are options 2 (Aluminum `Al^3+`) and 3 (Bismuth `Bi^3+`), as these ions will precipitate when `NH4Cl` and aqueous `NH3` are mixed.

### Final Answer:
The reagents `NH4Cl` and aqueous `NH3` will precipitate Aluminum (`Al^3+`) and Bismuth (`Bi^3+`) ions.

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