Hard water is not fit for washing clothes because

Options

A. (a) it contains `Na_(2)SO_(4)` and `KCl`
B. (b) it gives precipitate
C. (c) it contains impurities
D. (d) it is acidic in nature

Explanation

### Step-by-Step Solution:

1. **Understanding Hard Water**:
- Hard water is defined as water that contains high concentrations of dissolved minerals, primarily calcium (Ca²⁺) and magnesium (Mg²⁺) ions.

2. **Role of Soap in Washing**:
- Soap is a cleaning agent that works by forming micelles, which trap dirt and grease. The structure of soap consists of a long hydrophobic (water-repelling) alkyl chain and a hydrophilic (water-attracting) carboxylate group (–COO⁻).

3. **Reaction of Soap with Hard Water**:
- When soap is used in hard water, the calcium and magnesium ions react with the soap. This reaction leads to the formation of insoluble salts (scum), which can be represented as:
- For calcium: RCOO⁻Ca²⁺ → RCOO⁻Ca (precipitate)
- For magnesium: RCOO⁻Mg²⁺ → RCOO⁻Mg (precipitate)

4. **Formation of Scum**:
- The precipitates formed from the reaction of soap with calcium and magnesium ions are known as scum. This scum does not dissolve in water and thus reduces the effectiveness of soap.

5. **Conclusion**:
- The presence of calcium and magnesium ions in hard water leads to the formation of scum, which prevents soap from effectively cleaning clothes. Therefore, hard water is not suitable for washing clothes.

6. **Correct Answer**:
- Among the given options, the correct reason why hard water is not fit for washing clothes is that it gives precipitate (scum formation).