Vegetable oils and vanaspati ghee both contain long carbon chains, yet doctors advise against regular consumption of vanaspati ghee. (i) How does the chemical nature of the carbon chains differ between vegetable oil and vanaspati ghee? (ii) Explain what happens to vegetable oil during hydrogenation and why this change makes the product less healthy. (iii) Name the catalyst used in this process and state its role.
Generated by claude-sonnet-4-6 · 2026-06-26 01:11 · grounding rag
Model Answer
(i) Vegetable oils have long unsaturated carbon chains (contain C=C double bonds), whereas vanaspati ghee has saturated carbon chains (all single bonds), similar to animal fats.
(ii) During hydrogenation, hydrogen is added across the double bonds of unsaturated vegetable oil, converting it into a saturated fat (vanaspati ghee). Saturated fatty acids are considered harmful to health, making the hydrogenated product less healthy than the original oil.
(iii) The catalyst used is nickel (Ni). It speeds up the addition of hydrogen to the unsaturated carbon chains without itself being consumed in the reaction.
Source: Chapter 4, Section 4.3.3 Addition Reaction
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Explanation
- The examiner expects three distinct points matching the three sub-questions — don't merge them.
- Key terms to use: unsaturated, saturated, double bonds, hydrogenation, nickel catalyst.
- Avoid saying oils are "healthy" in general — the point is that saturated fats (product of hydrogenation) are harmful, not unsaturated ones.
- The role of catalyst is always: speeds up the reaction / causes it to proceed without being used up — state both parts for full credit.