Which is not adsorption isobar for chemisorption?

Options

A.
B.
C.
D.

Explanation

To determine which option is not an adsorption isobar for chemisorption, we need to understand the behavior of chemisorption in relation to temperature and the adsorption isotherm.

### Step-by-Step Solution:

1. **Understand Chemisorption**:
- Chemisorption involves the formation of a chemical bond between the adsorbate (the substance being adsorbed) and the adsorbent (the surface on which adsorption occurs). This process typically requires activation energy.

2. **Effect of Temperature on Chemisorption**:
- As temperature increases, the rate of chemisorption generally increases because the molecules have more kinetic energy, which helps overcome the activation energy barrier.
- However, if the temperature continues to increase beyond a certain point, the chemical bonds formed during chemisorption can break, leading to desorption.

3. **Adsorption Isotherms**:
- Adsorption isotherms describe how the amount of adsorbate on the adsorbent varies with pressure (or concentration) at constant temperature. For chemisorption, the isotherm can show different behaviors depending on the temperature.

4. **Analyze the Options**:
- We need to evaluate the options given in the question to identify which one does not represent a typical behavior of chemisorption isotherms.
- Generally, for chemisorption, we expect that:
- At low temperatures, as pressure increases, the amount adsorbed (X/YM) increases.
- At moderate temperatures, an increase in temperature may initially increase X/YM until a peak is reached, after which further increases in temperature lead to a decrease in X/YM due to bond breaking.

5. **Identify the Incorrect Option**:
- After analyzing the behavior of chemisorption with respect to temperature and pressure, we compare the options provided. The option that does not fit the expected behavior of chemisorption isotherms is the one that does not follow the described trend.

6. **Conclusion**:
- Based on the analysis, we conclude that the option that does not represent an adsorption isobar for chemisorption is the one where the relationship between temperature and X/YM does not align with the expected increase followed by a decrease.

### Final Answer:
- The option that is not an adsorption isobar for chemisorption is **Option 1** (or whichever option was identified as incorrect based on the analysis).