When bleaching powder is dissolved in water the residue left is

Options

A. `CaCl_(2)`
B. `Ca(ClO_(3))_(2)`
C. `CaO`
D. `Ca(OH)_(2)`

Explanation

To solve the question, "When bleaching powder is dissolved in water, what residue is left?", we can follow these steps:

### Step-by-Step Solution:

1. **Identify Bleaching Powder**:
- Bleaching powder is chemically known as calcium oxychloride, with the formula \( \text{Ca(OCl)}_2 \).
- It is commonly used as a disinfectant and bleaching agent.

2. **Dissolving in Water**:
- When bleaching powder is added to water, it undergoes a reaction. The chemical equation for this reaction can be represented as:
\[ \text{Ca(OCl)}_2 + 2 \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + 2 \text{Cl}_2 \uparrow \]
- Here, calcium hydroxide (\( \text{Ca(OH)}_2 \)) is formed, and chlorine gas (\( \text{Cl}_2 \)) is released as a byproduct.

3. **Identify the Residue**:
- The residue is the solid material that remains after the reaction. In this case, the solid that remains after the reaction is calcium hydroxide (\( \text{Ca(OH)}_2 \)).
- The chlorine gas that evolves does not contribute to the residue.

4. **Conclusion**:
- Therefore, the residue left after dissolving bleaching powder in water is calcium hydroxide (\( \text{Ca(OH)}_2 \)).

### Final Answer:
The residue left when bleaching powder is dissolved in water is \( \text{Ca(OH)}_2 \) (calcium hydroxide).

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