Temporary unstable hardness of water due to presence of :

Options

A. `CaCl_(2),MgSO_(4)`
B. `Ca^(+2),Mg^(+2)`
C. `K^(o+),CaCO_(3)`
D. `Ca(HCO_(3))_(2),Mg(HCO_(3))_(2)`

Explanation

**Step-by-Step Solution:**

1. **Understanding Hardness of Water:**
- Water can be classified into two types: soft water and hard water. Soft water contains sodium and potassium salts, while hard water contains salts of calcium and magnesium.

2. **Types of Hardness:**
- Hardness of water can be categorized into two types: temporary hardness and permanent hardness.
- Temporary hardness is primarily caused by the presence of bicarbonates of calcium and magnesium.
- Permanent hardness is due to the presence of chlorides and sulfates of calcium and magnesium.

3. **Identifying Temporary Hardness:**
- Temporary hardness is specifically due to the bicarbonate salts of calcium and magnesium. The chemical formulas for these bicarbonates are:
- Calcium bicarbonate: \( \text{Ca(HCO}_3\text{)}_2 \)
- Magnesium bicarbonate: \( \text{Mg(HCO}_3\text{)}_2 \)

4. **Reason for Temporary Hardness:**
- This type of hardness is termed "temporary" because it can be removed by boiling the water. When boiled, bicarbonates decompose to form carbonates, which precipitate out of the solution.

5. **Conclusion:**
- The presence of calcium bicarbonate and magnesium bicarbonate in water is what causes temporary unstable hardness. Therefore, the correct answer to the question is:
- **Option 4:** \( \text{Ca(HCO}_3\text{)}_2 \) and \( \text{Mg(HCO}_3\text{)}_2 \).

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