"Vegetable oils are hydrogenated by addition reaction". Explain this statement with the help of a chemical equation. Why are animal fats not hydrogenated? Out of vegetable oils and animal fats which one is preferred for cooking and why?

Explanation

### Step-by-Step Solution:

1. **Understanding Hydrogenation**:
- Hydrogenation is a chemical process that involves the addition of hydrogen (H₂) to unsaturated hydrocarbons (which contain double or triple bonds) to convert them into saturated hydrocarbons (which contain only single bonds). This process typically requires a catalyst, such as nickel (Ni).

2. **Chemical Equation**:
- Let's represent vegetable oil, which is an unsaturated hydrocarbon, as R-CH=CH-R' (where R and R' are hydrocarbon chains).
- The hydrogenation process can be represented as follows:
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