JEE Chemistry 2023 Question with Solution

Given: The reaction coordinate diagram from $A$ to $B$ has three peaks corresponding to Step I, Step II, and Step III.

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

In a reaction energy profile, intermediates are the species formed during the reaction and then consumed in later steps. They appear as the valleys between two successive peaks.

Here, the diagram shows two valleys, so the number of intermediates is $2$.

Activated complexes correspond to the transition states of each elementary step and appear at the peaks of the energy diagram.

Since the diagram has three peaks, the number of activated complexes is $3$.

The rate-determining step is the step with the highest activation energy barrier. Among the three peaks, the peak for Step II is the highest.

Therefore, Step II is the rate-determining step.

Therefore, the correct option is A: $2$ intermediates, $3$ activated complexes, and Step II as the rate-determining step.

Given: A three-step reaction energy diagram is provided.

Find: Count the valleys and peaks, then identify the highest barrier.

For a multistep reaction:

• each valley between peaks represents an intermediate
• each peak represents an activated complex or transition state

From the diagram:

• Number of valleys = $2$
• Number of peaks = $3$

Now compare the heights of the three peaks. The peak corresponding to Step II is the highest, so Step II has the largest activation energy.

Hence, the slowest step is Step II, which is the rate-determining step.

So the correct combination is $2$ intermediates, $3$ activated complexes, and II as the rate-determining step. The correct option is A.