Which plot is the adsorption isobar for chemisorption?

Options

A.
B.
C.
D.

Explanation

To determine which plot represents the adsorption isobar for chemisorption, we need to analyze the behavior of chemisorption with respect to temperature and the extent of adsorption.

### Step-by-Step Solution:

1. **Understanding Chemisorption**:
- Chemisorption is a type of adsorption that involves a chemical reaction between the adsorbate and the adsorbent. This process requires activation energy.

2. **Effect of Temperature on Chemisorption**:
- Initially, as the temperature increases, the extent of adsorption (X/M) also increases. This is because higher temperatures provide the necessary energy to overcome the activation energy barrier for the reaction.

3. **Reaching Equilibrium**:
- After reaching a certain point, the system reaches equilibrium. At this stage, the extent of adsorption reaches a maximum value.

4. **Post-Equilibrium Behavior**:
- Beyond this equilibrium point, if the temperature continues to increase, the extent of adsorption starts to decrease. This is because the increased kinetic energy at higher temperatures can lead to desorption, where the adsorbate molecules leave the surface of the adsorbent.

5. **Plotting the Relationship**:
- When we plot the extent of adsorption (X/M) against temperature, we will observe:
- An initial increase in X/M with temperature.
- A peak at the maximum extent of adsorption.
- A subsequent decrease in X/M as the temperature continues to rise beyond the equilibrium point.

6. **Identifying the Correct Plot**:
- Based on the described behavior, the correct plot for the adsorption isobar for chemisorption will show an initial increase followed by a decrease after reaching a maximum. This corresponds to a curve that rises to a peak and then falls.

### Conclusion:
- The correct plot that represents the adsorption isobar for chemisorption is **Plot B**, which illustrates the described behavior of extent of adsorption versus temperature.