Temporary hardness of water can be removed

Options

A. by passing `CO_(2)`
B. by passing `SO_(2)`
C. by adding `Ca(OH)_(2)`
D. by adding `NaCl`

Explanation

**Step-by-Step Solution:**

1. **Understanding Temporary Hardness**:
- Temporary hardness in water is primarily caused by the presence of bicarbonates of calcium (Ca(HCO₃)₂) and magnesium (Mg(HCO₃)₂).

2. **Identifying the Method for Removal**:
- To remove temporary hardness, we can use a method known as Clark's process, which involves the addition of calcium hydroxide (lime, Ca(OH)₂) to the water.

3. **The Chemical Reaction**:
- When calcium hydroxide is added to water containing calcium bicarbonate, a chemical reaction occurs:
\[ \text{Ca(HCO}_3\text{)}_2 + \text{Ca(OH)}_2 \rightarrow 2\text{CaCO}_3 \downarrow + 2\text{H}_2\text{O} \]
- In this reaction, calcium carbonate (CaCO₃) precipitates out of the solution, effectively removing the hardness.

4. **Reaction with Magnesium Bicarbonate**:
- Similarly, when magnesium bicarbonate reacts with calcium hydroxide, the following reaction occurs:
\[ \text{Mg(HCO}_3\text{)}_2 + \text{Ca(OH)}_2 \rightarrow \text{CaCO}_3 \downarrow + \text{MgCO}_3 \downarrow + 2\text{H}_2\text{O} \]
- Here, both calcium carbonate and magnesium carbonate precipitate out, further reducing the hardness of the water.

5. **Conclusion**:
- Therefore, the effective method to remove temporary hardness of water is by adding calcium hydroxide (lime).

**Final Answer**: Temporary hardness of water can be removed by adding calcium hydroxide (Ca(OH)₂).

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