Assertion : Detergents are preferred to soaps for washing purposes.
Reason : Detergents having branched chain hydrocarbon are non-biodegradable.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Detergents are preferred to soaps for washing purposes." This is true because detergents have better cleaning properties, especially in hard water, compared to soaps.

2. **Understanding the Reason**:
- The reason given is "Detergents having branched chain hydrocarbons are non-biodegradable." This is also true. Detergents with branched chains do not break down easily in the environment, which can lead to pollution.

3. **Comparison of Soaps and Detergents**:
- Soaps are made from the saponification of fats and oils, resulting in sodium or potassium salts of long-chain fatty acids. They work well in soft water but form insoluble precipitates (scum) when used in hard water.
- Detergents, on the other hand, are synthetic and can be used in both soft and hard water without forming scum. This is because they do not react with calcium and magnesium ions present in hard water.

4. **Biodegradability**:
- The assertion correctly identifies that detergents are preferred due to their effectiveness in various water types. However, the reason provided highlights a significant environmental concern. While some detergents are non-biodegradable (especially those with branched chains), there are also biodegradable detergents available.

5. **Conclusion**:
- Both the assertion and the reason are correct statements. However, the reason does not fully explain why detergents are preferred over soaps. The preference is primarily due to their ability to work in hard water, not solely because of their biodegradability.

### Final Answer:
- **Assertion**: True
- **Reason**: True
- **Explanation**: The assertion is correct, but the reason provided does not adequately explain the assertion.