Which cleansing agent gets precipitated in hard water ?

Options

A. Sodium lauryl sulphate
B. Sodium stearate
C. Cetyl trimethyl ammonium bromide
D. Sodium dodecylbenzesulphonate

Answer

To determine which cleansing agent gets precipitated in hard water, we need to analyze the options provided and understand the behavior of soaps and detergents in hard water.

### Step-by-Step Solution:

1. **Identify the Cleansing Agents**: The options provided are:
- Sodium Lauryl Sulfate
- Sodium Stearate
- Cetyl Trimethyl Ammonium Bromide
- Sodium Dodecyl Benzene Sulfonate

2. **Understand the Nature of Soaps and Detergents**:
- Soaps are typically sodium or potassium salts of long-chain fatty acids.
- Detergents, on the other hand, are synthetic cleansing agents that can function in hard water.

3. **Recognize the Effect of Hard Water**:
- Hard water contains ions such as calcium (Ca²⁺) and magnesium (Mg²⁺).
- When soap is added to hard water, the calcium and magnesium ions react with the soap, leading to the formation of insoluble salts (scum), which precipitate out of solution.

4. **Analyze Each Option**:
- **Sodium Lauryl Sulfate**: This is a detergent and does not precipitate in hard water.
- **Sodium Stearate**: This is a soap. When added to hard water, it reacts with calcium and magnesium ions to form insoluble calcium stearate and magnesium stearate, which precipitate.
- **Cetyl Trimethyl Ammonium Bromide**: This is a detergent and does not precipitate in hard water.
- **Sodium Dodecyl Benzene Sulfonate**: This is also a detergent and does not precipitate in hard water.

5. **Conclusion**: The only cleansing agent among the options that gets precipitated in hard water is **Sodium Stearate**.

### Final Answer:
**Sodium Stearate** is the cleansing agent that gets precipitated in hard water.

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