JEE Chemistry 2023 Question with Solution

Given: A reaction energy diagram shows conversion from $A$ to $B$ in three steps: I, II, and III.

Find: The number of intermediates, the number of activated complexes, and the rate-determining step.

Intermediates are species formed during a reaction that are subsequently consumed. In an energy profile, they are represented by the valleys between successive peaks. In the given diagram, there are two valleys, so there are $2$ intermediates.

Activated complexes are the transition states present at the top of each energy barrier. In the given diagram, there are three peaks, so there are $3$ activated complexes.

The rate-determining step is the slowest step, which corresponds to the step having the highest activation energy barrier. In the given diagram, Step II has the highest peak, so Step II is the rate-determining step.

Therefore, the correct option is A.

Given: The reaction proceeds in three steps and its energy profile contains three maxima and two minima between reactant $A$ and product $B$.

Find: Which option correctly matches the intermediates, activated complexes, and rate-determining step.

In a multi-step energy diagram:

• Each peak corresponds to one activated complex.
• Each valley between peaks corresponds to one intermediate.
• The highest barrier identifies the rate-determining step.

Applying this to the diagram:

• Number of peaks = $3$ $\Rightarrow$ number of activated complexes = $3$
• Number of valleys between peaks = $2$ $\Rightarrow$ number of intermediates = $2$
• Highest peak occurs in Step II $\Rightarrow$ rate-determining step = II

Hence, the correct combination is $2$ | $3$ | II, so the correct option is A.