What happens when hydrogen is added to a vegetable oil in the presence of nickel? Name the reaction and write one difference between the physical property of the vegetable oil and the product obtained in the reaction. Write the role of nickel in this reaction.

Explanation

### Step-by-Step Solution:

1. **Understanding the Reaction**: When hydrogen gas (H₂) is added to vegetable oil (which primarily consists of unsaturated fatty acids) in the presence of a catalyst like nickel, a chemical reaction occurs. This process is known as hydrogenation.

2. **Chemical Reaction**: The unsaturated bonds in the vegetable oil react with hydrogen. The general reaction can be represented as:
\[ \text{Vegetable Oil (Unsaturated)} + \text{H}_2 \xrightarrow{\text{Ni}} \text{Vegetable Ghee (Saturated)} \]
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