For an exothermic chemical process occurring in two as
(i) `A + B rarr X` (slow)
(ii) `X rarr AB` (fast)
The process of the reaction can be best described by

Options

A.
B.
C.
D. None of these

Answer

To solve the question regarding the exothermic chemical process occurring in two steps, we will analyze the reaction step by step.

### Step 1: Understanding the Reaction
The reaction is given in two steps:
1. \( A + B \rightarrow X \) (slow step)
2. \( X \rightarrow AB \) (fast step)

Since the overall reaction is exothermic, the energy of the products (AB) is lower than the energy of the reactants (A and B).

### Step 2: Energy Profile of the Reaction
In an exothermic reaction, the energy profile can be illustrated with a graph showing the energy of the reactants and products. The reactants will have higher energy than the products.

- **Reactants (A and B)**: Higher energy
- **Products (AB)**: Lower energy

### Step 3: Analyzing the Slow Step
The first step is slow, which means it has a higher activation energy (Ea). This is because slow reactions take longer to overcome the energy barrier.

- **Activation Energy for Step 1**: High
- **Graph Representation**: The first peak (for the slow step) will be higher.

### Step 4: Analyzing the Fast Step
The second step is fast, which means it has a lower activation energy. Fast reactions require less energy to proceed.

- **Activation Energy for Step 2**: Low
- **Graph Representation**: The second peak (for the fast step) will be lower than the first peak.

### Step 5: Constructing the Energy Profile Graph
Based on the above analysis, the energy profile graph will have:
- A higher peak for the slow step (first step).
- A lower peak for the fast step (second step).
- The overall energy level of the products will be lower than that of the reactants.

### Conclusion
The correct graph that represents this two-step exothermic reaction will show two peaks, with the first peak (slow step) being higher than the second peak (fast step).

The best description of the process of the reaction is represented by **Option B**.

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