select correct absorption isobars for chemisoption and physisoption respectivly ,
(where `x/m ` = extent of adsorption , T = temperature )

Options

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B.
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D.

Answer

To determine the correct absorption isobars for chemisorption and physisorption, we need to analyze how the extent of adsorption (x/m) varies with temperature (T) under constant pressure conditions.

### Step-by-Step Solution:

1. **Understanding Chemisorption**:
- Chemisorption involves the formation of strong chemical bonds between the adsorbate (the substance being adsorbed) and the adsorbent (the surface onto which it is adsorbed).
- Initially, as the temperature increases, the kinetic energy of the molecules increases, which can enhance the extent of adsorption (x/m) because more molecules can overcome the energy barrier to form bonds.

2. **Effect of Temperature on Chemisorption**:
- However, at higher temperatures, the increased molecular motion can lead to bond breaking, which decreases the extent of adsorption.
- Therefore, the graph for chemisorption will initially rise with temperature and then fall after reaching a peak. This indicates that there is an optimal temperature range for chemisorption.

3. **Understanding Physisorption**:
- Physisorption involves weak van der Waals forces between the adsorbate and adsorbent. This process is generally exothermic, meaning that it releases energy when adsorption occurs.
- As the temperature increases, the thermal energy can disrupt these weak interactions, leading to a decrease in the extent of adsorption.

4. **Effect of Temperature on Physisorption**:
- For physisorption, as the temperature increases, the extent of adsorption (x/m) decreases continuously because the thermal energy overcomes the weak forces holding the adsorbate to the adsorbent.
- Thus, the graph for physisorption will show a continuous decline in the extent of adsorption with increasing temperature.

5. **Selecting the Correct Isobars**:
- Based on the above analysis, we can conclude:
- For chemisorption, the graph will initially increase and then decrease (indicating a peak).
- For physisorption, the graph will continuously decrease with increasing temperature.
- Therefore, the correct absorption isobars for chemisorption and physisorption respectively would be the one that shows these characteristics.

### Conclusion:
The correct absorption isobars for chemisorption and physisorption are:
- Chemisorption: Initially increases and then decreases with temperature.
- Physisorption: Continuously decreases with increasing temperature.