CBSE Class 10 Science 2018 · Paper 31/1/C · Question 8

When hydrogen is added to a vegetable oil in the presence of nickel, the hydrogen adds to the carbon-carbon double bonds of the unsaturated oil, and the oil changes into a saturated fat, vegetable ghee (vanaspati): ${\text{R}}_2{\text{C=CR}}_2+{\text{H}}_2\stackrel{\text{Ni}}{\to }{\text{R}}_2{\text{CH-CHR}}_2$. Name of the reaction: hydrogenation (an addition reaction). Difference: the vegetable oil is a liquid at room temperature, whereas the product, vegetable ghee, is a solid at room temperature. Role of nickel: it is a catalyst; it speeds up the addition of hydrogen without itself being used up in the reaction.