Which of the following is not precipitate by `H_(2)S` in presence of `NH_(3)`

Options

A. `Ca^(2+)`
B. `Mn^(2+)`
C. `Fe^(3+)`
D. `Cd^(2+)`

Answer

To determine which of the following cations is not precipitated by H₂S in the presence of NH₃, we need to analyze the behavior of each cation with respect to their group classification in qualitative analysis.

### Step-by-Step Solution:

1. **Identify the Cations**: The cations given in the question are:
- Calcium (Ca²⁺)
- Manganese (Mn²⁺)
- Iron (Fe³⁺)
- Cadmium (Cd²⁺)

2. **Understand the Group Classification**: In qualitative inorganic analysis, cations are classified into different groups based on their behavior towards specific reagents. H₂S in the presence of NH₃ is used to precipitate certain cations.

3. **Group 3 Cations**: H₂S in a basic medium (NH₃) is a group reagent for Group 3 cations. The typical cations that precipitate as sulfides in this group include:
- Al³⁺
- Fe³⁺
- Mn²⁺
- Cu²⁺
- Zn²⁺

4. **Cation Behavior**:
- **Calcium (Ca²⁺)**: Calcium is classified under Group 4 cations. It does not precipitate with H₂S in the presence of NH₃.
- **Manganese (Mn²⁺)**: Manganese is a Group 3 cation and will precipitate as manganese sulfide (MnS) in the presence of H₂S and NH₃.
- **Iron (Fe³⁺)**: Iron is also a Group 3 cation and will precipitate as iron sulfide (Fe₂S₃) in the presence of H₂S and NH₃.
- **Cadmium (Cd²⁺)**: Cadmium is classified under Group 2 cations and will not precipitate with H₂S in a basic medium.

5. **Conclusion**: The cations that do not precipitate with H₂S in the presence of NH₃ are Calcium (Ca²⁺) and Cadmium (Cd²⁺). Therefore, the answer to the question is:
- Calcium (Ca²⁺) and Cadmium (Cd²⁺) are not precipitated by H₂S in the presence of NH₃.

### Final Answer:
Calcium (Ca²⁺) and Cadmium (Cd²⁺) are not precipitated by H₂S in the presence of NH₃.