Match List I with List II
| List I | List II |
| A. Elementary Reactions | I. No energy of activation |
| B. Complex Reactions | II. Single step |
| C. Free radical combination | III. High energy of activation |
| D. Slow Reaction | IV. Several elementary steps |
Choose the correct options from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-II, B-IV, C-I, D-III
A reaction that takes place in one step is an elementary reaction; a reaction that goes through a sequence of elementary steps (its mechanism) is a complex reaction. The rate of a step depends on its activation energy: the higher the barrier, the slower the reaction.
(A) Elementary Reactions — This matches (II) Single step. The reactants turn into products in one step.
(B) Complex Reactions — This matches (IV) Several elementary steps. The sequence of elementary steps is the mechanism of the reaction.
(C) Free radical combination — This matches (I) No energy of activation. Two radicals join without any bond being broken, so there is practically no barrier.
(D) Slow Reaction — This matches (III) High energy of activation. By \( k = A\,e^{-E_a/RT} \), a large \( E_a \) gives a small rate constant, because few molecules have enough energy to cross the barrier.