Yellow coloured solution of `FeCl_(3)` changes in light green when

Options

A. `SnCl_(2)` is added
B. `Zn` is added
C. `H_(2)S` gas is added
D. All true

Answer

To solve the question regarding the yellow colored solution of `FeCl3` changing to light green, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Initial State**:
- The yellow colored solution is due to the presence of ferric ions (Fe³⁺) in `FeCl3`.

2. **Identify the Target State**:
- The light green color corresponds to ferrous ions (Fe²⁺) in `FeCl2`.

3. **Understand the Chemical Change**:
- The change from yellow to light green indicates a reduction process where Fe³⁺ is being reduced to Fe²⁺.

4. **Identify Reducing Agents**:
- To reduce Fe³⁺ to Fe²⁺, a reducing agent is required. The options provided are:
- SnCl₂ (Stannous chloride)
- Zn (Zinc)
- H₂S (Hydrogen sulfide)

5. **Evaluate Each Option**:
- **SnCl₂**: This is a known reducing agent that can reduce Fe³⁺ to Fe²⁺.
- **Zn**: Zinc is also a reducing agent and can facilitate the reduction of Fe³⁺ to Fe²⁺.
- **H₂S**: Hydrogen sulfide can act as a reducing agent and can reduce Fe³⁺ to Fe²⁺ as well.

6. **Conclusion**:
- Since all three substances (SnCl₂, Zn, H₂S) can act as reducing agents to convert Fe³⁺ to Fe²⁺, the correct answer is that the yellow solution of `FeCl3` changes to light green when any of these reducing agents are added.

### Final Answer:
- The yellow colored solution of `FeCl3` changes to light green when SnCl₂, Zn, or H₂S is added. Therefore, the correct option is **all are true**.

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