(a) In some reactions, the energy possessed by colliding molecules is more than the threshold energy, yet the reaction is slow. Why? (b) State one condition in which a bimolecular reaction may be kinetically of the first order.
Answers
Hi! the answer of Ques. (a) is :
● Having energy more than the threshold energy can increase the number or frequency of collisions between the reactants.
● But to form the activated complex, the colliding reactants also need to have favourable orientation between themselves. This depends on the structure and geometry of the reactant molecules. Certain structural features can sterically hinder the occurrence of effective or successful collisions between them.
● Therefore, certain reactions may not proceed at a faster rate even when the reactants have sufficient threshold energy.
And the second's is :
● A bimolecular reaction can be kinetically first order in behaviour provided one of the reactants is taken in such a large excess that its concentration may hardly change. ... Thus, a bimolecular reaction will be of first order. These reactions are known as pseudo chemical reactions.
Hope, it helped you.