Q.What do you mean by activity and selectivity of catalysts?

Step 1 – Activity. The activity of a catalyst is its capacity to accelerate a chemical reaction. It depends on the strength of adsorption of the reactants on its surface: adsorption must be strong enough to activate the reactants but not so strong that products cannot desorb. For example, hydrogenation of ethene is accelerated enormously (up to $10^{6}$–$10^{10}$ times) in the presence of a metal catalyst like $Pt$.

Step 2 – Selectivity. The selectivity of a catalyst is its ability to direct a reaction to form specific products. The same reactants can give different products with different catalysts, e.g. carbon monoxide and hydrogen:

$CO + H_2 \xrightarrow{Cu} HCHO$ …

Define the two catalyst properties separately: activity (rate enhancement, governed by adsorption strength) and selectivity (product dire …

• Using activity and selectivity interchangeably.
• Forgetting to show that selectivity means different products with different catalysts. …