Organic chemistry: hydrogenation of oils MCQ - Practice Questions with Answers

When vegetable oils react with hydrogen in the presence of nickel, hydrogen atoms add across the carbon-carbon double bonds of unsaturated oil molecules. This hydrogenation converts liquid oils into more saturated, solid fats, so it is an addition reaction. A substitution reaction would replace one atom or group with another, which is not happening here. A displacement reaction involves one element replacing another in a compound. Oxidation would involve addition of oxygen, removal of hydrogen, or increase in oxidation state, whereas this process adds hydrogen.