Permanenet hardcore of water is removed by aciding

Answer

To solve the question regarding the removal of permanent hardness of water, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Hardness**:
- There are two types of hardness in water: temporary hardness and permanent hardness.
- Temporary hardness is primarily caused by the presence of bicarbonates of calcium and magnesium (e.g., calcium bicarbonate, magnesium bicarbonate).
- Permanent hardness is caused by the presence of chlorides and sulfates of calcium and magnesium (e.g., calcium chloride, magnesium chloride, calcium sulfate, magnesium sulfate).

**Hint**: Remember the sources of hardness; bicarbonates lead to temporary hardness, while chlorides and sulfates lead to permanent hardness.

2. **Methods of Removal**:
- Temporary hardness can be removed by boiling or using Clark's method, which involves adding slaked lime (calcium hydroxide) to precipitate calcium carbonate.
- Permanent hardness cannot be removed by boiling and requires different methods.

**Hint**: Focus on the specific methods used for each type of hardness; boiling works for temporary hardness, not for permanent hardness.

3. **Identify the Correct Chemical**:
- Among the options given (sodium bicarbonate, washing soda, and calcium hydroxide), we need to determine which one can remove permanent hardness.
- Sodium bicarbonate does not remove any type of hardness.
- Calcium hydroxide is used in Clark's method, which is for temporary hardness.
- Washing soda (sodium carbonate) can react with the chlorides and sulfates present in permanent hardness to form insoluble precipitates (like calcium carbonate).

**Hint**: Recall that washing soda can be used for both types of hardness, but it is particularly effective for permanent hardness.

4. **Conclusion**:
- The correct answer to the question is that permanent hardness of water is removed by washing soda (sodium carbonate).

**Final Answer**: The option that removes permanent hardness of water is **washing soda**.