For an exothermic chemical process ocuuring in two process occuring in two steps as follows
`(i)A+BtoX("slow")" "(ii)XtoAB("fast")`
The progress of reaction can be best described by :

Options

A.
B.
C.
D.

Answer

To solve the problem regarding the progress of an exothermic chemical process occurring in two steps, we need to analyze the given reactions and their characteristics.

### Step-by-Step Solution:

1. **Identify the Reactions**:
- The first reaction is \( A + B \rightarrow X \) (slow step).
- The second reaction is \( X \rightarrow AB \) (fast step).

2. **Determine the Rate-Determining Step**:
- Since the first step is the slow step, it is the rate-determining step (RDS). This means that the energy barrier for this step is higher compared to the second step.

3. **Understand Exothermic Reactions**:
- In an exothermic reaction, the energy of the products is lower than that of the reactants because energy is released during the reaction. Therefore, the products are more stable.

4. **Graphical Representation**:
- We need to plot a potential energy diagram for the reaction:
- The energy of reactants \( A + B \) will be higher than that of the product \( AB \).
- The transition state for the first step (from \( A + B \) to \( X \)) will have a high energy peak because it is the slow step.
- The transition state for the second step (from \( X \) to \( AB \)) will have a lower energy peak since it is the fast step.

5. **Drawing the Energy Diagram**:
- Start with a high energy level for the reactants \( A + B \).
- Draw a peak for the transition state of the first step (high energy).
- After the peak, drop down to a lower energy level for the intermediate \( X \).
- Then, from \( X \), draw a smaller peak for the transition state of the second step (lower energy).
- Finally, drop down to an even lower energy level for the products \( AB \).

6. **Conclusion**:
- The correct graph will show that the energy of the reactants is higher than the energy of the products, with the first transition state being the highest point on the graph, followed by a lower transition state for the second step.

### Final Answer:
The progress of the reaction can be best described by graph **C**, which shows the energy of reactants higher than that of the products, with the appropriate energy peaks for the transition states.