Vegetable oils are hydrogenated industrially to produce vanaspati ghee.
(i) Name the catalyst used.
(ii) Write the chemical equation for the hydrogenation of ethene as an example of this type of reaction.
(iii) Why is it advisable to use oils containing unsaturated fatty acids rather than animal fats for cooking?
Generated by claude-sonnet-4-6 · 2026-06-26 01:07 · grounding rag
Model Answer
(i) The catalyst used is nickel (Ni).
(ii) Chemical equation for hydrogenation of ethene:
$$\text{CH}_2{=}\text{CH}_2 + \text{H}_2 \xrightarrow{\text{Ni, heat}} \text{CH}_3\text{-}\text{CH}_3$$
(Ethene → Ethane)
(iii) Animal fats contain saturated fatty acids, which are harmful to health. Oils with unsaturated fatty acids are healthier and therefore advisable for cooking.
Source: Chapter 4, Section 4.3.3 Addition Reaction
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Explanation
- (i) Both Ni and Pd are acceptable, but the passage specifically highlights nickel for the industrial hydrogenation of vegetable oils — write Ni for full marks.
- (ii) Show the double bond in ethene, the reagent H₂, the catalyst (Ni) above the arrow, and the product ethane. Writing structural or molecular formulae both earn marks, but showing the double bond clearly is important.
- (iii) The key contrast examiners look for: saturated (animal fats) = harmful; unsaturated (vegetable oils) = healthier. One sentence is enough for 1 mark.