Hydrogenation of vegetable oils using nickel catalyst is an example of
- A.Substitution reaction.
- B.Elimination reaction.
- C.Addition reaction.
- D.Free-radical polymerization.
Correct answer
Explanation
The correct answer is C, Addition reaction. Hydrogen adds across the carbon–carbon double bonds of the oil.
Vegetable oils are unsaturated: their fatty acid chains contain C=C double bonds, which keep them liquid. When hydrogen gas is passed through the heated oil with finely divided nickel as a catalyst, hydrogen atoms add to the double bonds and turn them into single bonds. The saturated product is a solid fat, which is how vanaspati ghee is made. Partial hydrogenation also forms trans fats, which are harmful to the heart.
A is wrong because in substitution one atom replaces another, as when chlorine replaces hydrogen in methane in sunlight.
B is wrong because elimination removes atoms and creates a double bond, the reverse of what happens here.
D is wrong because no long chain of repeating units (a polymer) is formed.
Exam tip: unsaturated oil + H₂ (nickel catalyst) → saturated fat (vanaspati), an addition reaction; saturated compounds give substitution reactions.
Practice Questions
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- B.2 and 3 only
- C.1 only
- D.1, 2 and 3
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- B.-100 °C
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- D.-173.15 °C
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- A.the reaction requires initiation by a catalyst
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- B.a deflecting force towards east direction.
- C.a deflecting force towards west direction.
- D.no deflecting force.
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