What is the use of Clark's method?

Options

A. Remove temporary hardness of water by adding quick lime or slaked lime
B. Remove permanent hardness by adding washing soda
C. Remove permanent hardness by adding permutit.
D. Remove temporary hardness by boiling

Answer

**Step-by-Step Solution:**

1. **Understanding Clark's Method**: Clark's method is a process used to treat water, specifically to address the issue of temporary hardness.

2. **Temporary Hardness**: Temporary hardness in water is primarily caused by the presence of bicarbonates and carbonates of calcium and magnesium. This type of hardness can be removed by boiling the water or by adding certain chemicals.

3. **Chemical Reaction Involved**: In Clark's method, calcium hydroxide (commonly known as lime) is added to the water. The chemical reaction can be represented as follows:
\[ \text{Ca(HCO}_3\text{)}_2 + \text{Ca(OH)}_2 \rightarrow 2 \text{CaCO}_3 + 2 \text{H}_2\text{O} \]
Here, calcium bicarbonate reacts with calcium hydroxide to form calcium carbonate and water.

4. **Outcome of the Reaction**: The calcium carbonate formed is insoluble in water and precipitates out, effectively removing the hardness from the water.

5. **Conclusion**: Therefore, the primary use of Clark's method is to remove temporary hardness from water by adding quicklime (calcium hydroxide).

**Final Answer**: Clark's method is used to remove temporary hardness of water by adding quicklime (calcium hydroxide).

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