Permanent hardness of water is due to the presence of

Options

A. Sulphates of Mg and Ca
B. Bicarbonates of mg and Ca
C. Sulphates of Na and K
D. Bicarbonates of Na and K

Answer

**Step-by-Step Solution:**

1. **Understanding Water Hardness:**
- Water hardness is classified into two types: temporary hardness and permanent hardness.
- Temporary hardness is primarily caused by the presence of bicarbonates of calcium and magnesium.

2. **Identifying Permanent Hardness:**
- Permanent hardness is caused by the presence of chlorides and sulfates of calcium and magnesium.
- Common compounds responsible for permanent hardness include calcium sulfate (CaSO₄), magnesium sulfate (MgSO₄), calcium chloride (CaCl₂), and magnesium chloride (MgCl₂).

3. **Analyzing the Options:**
- Option 1: Sulfates of magnesium and calcium - This is correct as these compounds contribute to permanent hardness.
- Option 2: Bicarbonates of magnesium and calcium - This is incorrect as these compounds contribute to temporary hardness.
- Option 3: Sulfates of sodium and potassium - This is incorrect as sodium and potassium do not contribute to permanent hardness in the same way.
- Option 4: Bicarbonates of sodium and potassium - This is also incorrect as these compounds do not contribute to hardness.

4. **Conclusion:**
- The correct answer is option 1: "Sulfates of magnesium and calcium" are responsible for the permanent hardness of water.

**Final Answer:**
Permanent hardness of water is due to the presence of sulfates of magnesium and calcium.

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