Question

What do you mean by activity and selectivity of catalyst?

Answer 1

1. Activity of Catalyst: The activity of a catalyst is its ability to increase the rate of a particular reaction, Chemisorption is the main factor in deciding the activity of a catalyst. The adsorption of reactants on the catalyst surface should be neither too strong nor too weak. It should just be strong enough to make the catalyst active.

2. Selectivity of catalyst: The ability of the catalyst to direct a reaction to yield a particular product is referred to as the selectivity of the catalyst. For example, by using different catalysts, we can get different products for the reaction between H₂ and CO.

(i) \[\ce{CO_{(g)} + 3H2_{(g)} ->[Ni] CH4_{(g)} + H2O_{(g)}}\]

(ii) \[\ce{CO_{(g)} + 2H2_{(g)} ->[Cu/ZnO][CrO3] CH3OH_{(g)}}\]

(iii) \[\ce{CO_{(g)} + H2_{(g)} ->[Cu] HCHO_{(g)}}\]