Efflorescence is shown by

Options

A. bleaching powder
B. baking soda
C. washing soda
D. plaster of Paris

Answer

To solve the question regarding which compound shows efflorescence, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Efflorescence**:
- Efflorescence is the process where a hydrated salt loses its water of crystallization when exposed to air.

2. **Identify Hydrated Salts**:
- Look for compounds that are hydrated salts, which means they contain water molecules in their crystalline structure.

3. **Examine the Given Compounds**:
- Among the options provided, identify the compound that is a hydrated salt. For example, washing soda, which has the formula Na2Cu3.10H2O, is a hydrated salt.

4. **Analyze the Process**:
- When washing soda is exposed to air, it can lose water molecules. The chemical reaction can be represented as:
\[ \text{Na}_2\text{Cu}_3\cdot10\text{H}_2\text{O} \rightarrow \text{Na}_2\text{Cu}_3\cdot\text{H}_2\text{O} + 9\text{H}_2\text{O} \]
- This shows that it loses 9 water molecules, demonstrating the process of efflorescence.

5. **Conclude the Answer**:
- Since washing soda is the compound that undergoes efflorescence by losing water of crystallization, the answer to the question is washing soda.

### Final Answer:
- **Washing soda (Na2Cu3.10H2O) shows efflorescence.**

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