Only temporary hardness of water is removed by

Options

A. calgon's method
B. clark's method
C. lon-exchange method
D. synthetic resins method

Answer

To solve the question regarding which method removes only temporary hardness of water, we will analyze each of the methods mentioned in the question.

### Step-by-Step Solution:

1. **Understanding Temporary Hardness**:
- Temporary hardness of water is primarily due to the presence of bicarbonates of calcium and magnesium. It can be removed by boiling or by adding certain chemicals.

2. **Analyzing Calgan's Method**:
- Calgan's method involves the use of sodium hexametaphosphate (NaPO3)6, which is effective in removing permanent hardness by adsorbing calcium and magnesium ions.
- **Conclusion**: This method is not suitable for removing temporary hardness.

3. **Analyzing Clarke's Method**:
- Clarke's method specifically targets temporary hardness. It involves the reaction of bicarbonates of calcium and magnesium with slaked lime (Ca(OH)2).
- The reaction leads to the formation of calcium carbonate (CaCO3), which precipitates out, effectively removing the hardness.
- **Conclusion**: This method is correct for removing temporary hardness.

4. **Analyzing Ion Exchange Method**:
- The ion exchange method uses resins to exchange calcium and magnesium ions with sodium or potassium ions. This method is primarily used for the removal of permanent hardness.
- **Conclusion**: This method does not remove temporary hardness.

5. **Analyzing Synthetic Resin Method**:
- Similar to the ion exchange method, synthetic resin methods are also used to remove permanent hardness. They involve the exchange of hardness ions with sodium ions.
- **Conclusion**: This method is not suitable for removing temporary hardness.

### Final Answer:
The method that removes only temporary hardness of water is **Clark's method**.