Question

Answer the following in brief.

How a catalyst increases the rate of reaction? Explain with the help of a potential energy diagram for catalyzed and uncatalyzed reactions.

Answer 1

i. A catalyst provides an alternative pathway associated with lower activation energy.

Potential energy barriers for catalyzed and uncatalyzed reactions

ii. The potential energy diagram compares the potential energy barriers for the catalysed and uncatalysed reactions. The barrier for uncatalysed reaction (E_a) is larger than that for the same reaction in the presence of a catalyst E_a.

iii. Consider the decomposition of H₂O₂ in aqueous solution catalysed by I^- ions \[\ce{2H2O_2_{(l)}->[I-]2H2O_{(l)} + O_{2(g)}}\].

At room temperature, the rate of reaction is slower in the absence of a catalyst with its activation energy being 76 kJ mol^-1. In the presence of catalyst, iodide ion (I^- ), the reaction is faster since the activation energy decreases to 57 kJ mol^-1.