Which of the following is correct for the decrease in the physical adsorption with increase of temperature

Options

A. Adsorption process is exothermic and according to Lechatelier principle the physical adsorption decreases with increase in temperature .
B. Physical adsorption is endothermic
C. Physical adsorption occurs at high temperature
D. all of these

Explanation

To solve the question regarding the decrease in physical adsorption with an increase in temperature, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Physical Adsorption**:
- Physical adsorption (physisorption) is a process where gas molecules adhere to a solid surface through weak van der Waals forces.

2. **Nature of Physical Adsorption**:
- This process is exothermic, meaning it releases heat. When gas molecules are adsorbed onto a surface, energy is released due to the formation of intermolecular forces.

3. **Effect of Temperature on Physical Adsorption**:
- According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in temperature, the system will adjust to counteract that change.
- For an exothermic process, increasing the temperature will shift the equilibrium to favor the reactants (in this case, the gas phase), thus decreasing the extent of adsorption.

4. **Entropy Considerations**:
- The process of adsorption decreases the entropy (degree of randomness) of the system because gas molecules become more ordered when they are adsorbed onto a surface.
- Since entropy decreases, the change in entropy (ΔS) is negative.

5. **Gibbs Free Energy (ΔG)**:
- The relationship between Gibbs free energy, enthalpy, and entropy is given by the equation:
\[ \Delta G = \Delta H - T\Delta S \]
- For physical adsorption, ΔH is negative (exothermic) and ΔS is negative. As temperature (T) increases, the term \(T\Delta S\) becomes more positive, which can make ΔG positive, indicating a non-spontaneous process.

6. **Conclusion**:
- Therefore, as the temperature increases, physical adsorption decreases because the process is exothermic. The correct conclusion is that physical adsorption decreases with an increase in temperature.

### Final Answer:
- The correct statement is: "Adsorption is an exothermic process, and physical adsorption decreases with an increase in temperature."