For an exothermic reaction, following two steps are involved.
`"Step 1. "A +B rarrI" (slow)"`
`"Step 2. "IrarrAB" (fast)"`
Which of the following graphs correctly represent this reaction ?

Options

A.
B.
C.
D.

Answer

To solve the problem regarding the exothermic reaction with the given steps, we will analyze the reaction mechanism and how it reflects on a potential energy diagram.

### Step 1: Understand the Reaction Steps
- The reaction consists of two steps:
- **Step 1:** \( A + B \rightarrow I \) (slow)
- **Step 2:** \( I \rightarrow AB \) (fast)

### Step 2: Identify the Nature of the Reaction
- Since the reaction is exothermic, the overall energy of the products (AB) will be lower than that of the reactants (A + B).

### Step 3: Analyze the Energy Profile
- In an energy profile diagram for a reaction:
- The y-axis represents potential energy.
- The x-axis represents the progress of the reaction.
- For an exothermic reaction, the energy of the products is lower than that of the reactants.

### Step 4: Determine the Number of Maxima and Minima
- The number of maxima in the energy diagram corresponds to the number of steps in the reaction mechanism.
- In this case, there are two steps, so we expect two maxima (one for each step).
- Between these two maxima, there will be a valley representing the stable intermediate \( I \).

### Step 5: Activation Energy Consideration
- The activation energy for the slow step (Step 1) will be higher than for the fast step (Step 2).
- This means that the first peak (for Step 1) will be higher than the second peak (for Step 2).

### Step 6: Conclusion
- The correct graph must show:
- Two peaks (maxima) corresponding to the two steps.
- The first peak higher than the second peak.
- The overall energy of the products lower than the reactants.

### Final Answer
Based on the analysis, the correct graph that represents this exothermic reaction mechanism is **Option 2**.