A black sulphide is formed by the action of `H_(2)S` on:

Options

A. cupric chloride
B. cadmium chloride
C. zinc chloride
D. ferric chloride

Explanation

To determine which compound forms a black sulfide when reacted with hydrogen sulfide (H₂S), we can analyze the interaction of H₂S with various metal chlorides. Here’s a step-by-step solution:

### Step 1: Identify the metal chlorides
We will consider the following metal chlorides:
1. Cupric chloride (CuCl₂)
2. Cadmium chloride (CdCl₂)
3. Zinc chloride (ZnCl₂)
4. Ferric chloride (FeCl₃)

### Step 2: React H₂S with each metal chloride
We will examine the reaction of H₂S with each of these metal chlorides to see if a black sulfide is formed.

1. **Cupric chloride (CuCl₂)**:
- Reaction:
\[ \text{Cu}^{2+} + \text{S}^{2-} \rightarrow \text{CuS} \]
- Result: CuS is formed, which is black in color.

2. **Cadmium chloride (CdCl₂)**:
- Reaction:
\[ \text{Cd}^{2+} + \text{S}^{2-} \rightarrow \text{CdS} \]
- Result: CdS is formed, which is yellow in color.

3. **Zinc chloride (ZnCl₂)**:
- Reaction:
\[ \text{Zn}^{2+} + \text{S}^{2-} \rightarrow \text{ZnS} \]
- Result: ZnS is formed, which is white in color.

4. **Ferric chloride (FeCl₃)**:
- Reaction:
\[ \text{Fe}^{3+} + \text{S}^{2-} \rightarrow \text{Fe}^{2+} + \text{S} + 2\text{H}^{+} \]
- Result: Elemental sulfur (S) is formed, which is milky white in color.

### Step 3: Conclusion
From the reactions above, only the reaction between H₂S and cupric chloride (CuCl₂) results in the formation of a black sulfide (CuS). Therefore, the answer to the question is:

**A black sulfide is formed by the action of H₂S on cupric chloride (CuCl₂).**

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