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A catalyst increases the rate of a reaction while an inhibitor decreases it. A promoter cannot catalyse a reaction on its own without the presence of a catalyst. The activity of enzyme catalysts increases in the presence of metal ions like Mn2+ and Co2+. When a solid catalyst is used for a gaseous reaction, energy released in physisorption increases the rate of reaction. Which of the following statements about catalysts and catalytic action is NOT true?

1. A catalyst increases the rate of a reaction while inhibitor decreases the reaction rate.
2. A promoter cannot catalyse the reaction on its own without the presence of catalyst.
3. The activity of enzyme catalysts increases in presence of metal ions like Mn2+, Co2+ etc.
4. When a solid catalyst is used for gaseous reaction, energy released in physisorption increases the rate of reaction.

Correct answer: When a solid catalyst is used for gaseous reaction, energy released in physisorption increases the rate of reaction.

Solution

In heterogeneous catalysis, it is chemisorption — not physisorption — that weakens and activates the bonds in the reactant molecules, thereby increasing the rate. Physisorption merely concentrates reactants on the surface without activating them. So the statement about physisorption is not true.

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