The soap can be hardened by

Options

A. adding sodium carbonate or sodium silicate during its manufacture
B. adding sodium chloride
C. adding potassium hydroxide
D. adding animal fat and coconut oil

Answer

### Step-by-Step Solution:

1. **Understanding Soap Formation**:
- Soap is produced through a chemical process called saponification. This involves the reaction of fats or oils (which are triglycerides) with a strong base.

2. **Saponification Process**:
- The triglycerides are heated with a strong base, commonly sodium hydroxide (NaOH). During this reaction, the triglycerides break down, and soap is formed along with glycerol as a by-product.

3. **Harden Soap**:
- To harden the soap, certain additives can be introduced during the manufacturing process. The most common substances used for this purpose are sodium chloride (NaCl) and sodium silicate.

4. **Salting Out Process**:
- The addition of saturated sodium chloride (common salt) or sodium silicate helps in precipitating the soap out of the solution, making it firmer and more solid in texture.

5. **Conclusion**:
- Therefore, soap can be hardened by adding sodium carbonate or sodium silicate during its manufacturing process.

### Final Answer:
The soap can be hardened by adding sodium carbonate or sodium silicate during its manufacture.

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