Soaps do not work in hard water containing calcium and magnesium ions because

Options

A. `Ca^(2+) and Mg^(2+)` ion form insoluble calcium and magnesium salts in the form of scum
B. `Na^(+) and K^(+)` present in soap react with `Ca^(2+) and Mg^(2+)` and hinder cleansing process
C. a large amount of soap is to be used in presence of ` Ca^(2+) and Mg^(2+)`
D. scum formed by combination of `Na^(+),Ca^(2+) and Mg^(2+)` stick to the cloth and are not removed on agitations.

Explanation

### Step-by-Step Solution:

1. **Understanding Hard Water**: Hard water contains high concentrations of calcium (Ca²⁺) and magnesium (Mg²⁺) ions. These ions can interfere with the cleaning action of soaps.

2. **Composition of Soap**: Soap is typically a sodium salt of fatty acids, such as sodium stearate (C₁₇H₃₅COONa). When soap is dissolved in water, it dissociates into sodium ions (Na⁺) and stearate ions (C₁₇H₃₅COO⁻).

3. **Reaction with Hard Water**: When soap is added to hard water, the calcium and magnesium ions react with the stearate ions to form insoluble salts, specifically calcium stearate (Ca(C₁₇H₃₅COO)₂) and magnesium stearate (Mg(C₁₇H₃₅COO)₂).

4. **Formation of Scum**: The insoluble calcium and magnesium salts precipitate out of the solution, forming a substance known as scum. This scum does not contribute to the cleaning process and can coat fabrics, making them feel greasy.

5. **Conclusion**: The presence of calcium and magnesium ions in hard water leads to the formation of insoluble salts with soap, rendering the soap ineffective as a cleaning agent. Therefore, the correct answer to the question is that soaps do not work in hard water because calcium and magnesium ions form insoluble salts, which appear as scum.

### Final Answer:
Soaps do not work in hard water containing calcium and magnesium ions because they form insoluble calcium and magnesium salts (scum) that are ineffective for cleaning.