Which one of the following characteristics is not correct for physical adsorption? 

Options

A. a. Adsorption increases with increases in temperature
B. b. Adsorption is spontaneous
C. c. Both enthalpy and entropy of adsorption are negative
D. d. Adsorption on solids is reversible

Answer

To determine which characteristic is not correct for physical adsorption, we can analyze each statement provided in the question.

### Step-by-Step Solution:

1. **Understanding Physical Adsorption**:
- Physical adsorption, also known as physisorption, involves weak van der Waals forces between the adsorbate and the adsorbent. It typically occurs at lower temperatures and is characterized by a reversible process.

2. **Analyzing Statement A**:
- **Statement A**: "Exorption increases with the increase in temperature."
- This statement is incorrect. In physical adsorption, as temperature increases, the adsorption process decreases because the kinetic energy of the molecules increases, leading to desorption (exorption). Thus, this statement is not true for physical adsorption.

3. **Analyzing Statement B**:
- **Statement B**: "Adsorption is spontaneous."
- This statement is correct. Physical adsorption is generally spontaneous, meaning it occurs naturally without the need for external energy.

4. **Analyzing Statement C**:
- **Statement C**: "Both enthalpy and entropy of the adsorption are negative."
- This statement is also correct. In physical adsorption, the process is exothermic (negative enthalpy change) and leads to a decrease in randomness (negative entropy change).

5. **Analyzing Statement D**:
- **Statement D**: "Exorption on solid is reversible."
- This statement is correct as well. Physical adsorption is a reversible process, meaning that adsorbed molecules can be released back into the gas or liquid phase.

6. **Conclusion**:
- The only statement that is not correct regarding physical adsorption is **Statement A**. Therefore, the answer to the question is **A**.

### Final Answer:
The characteristic that is not correct for physical adsorption is **A**: "Exorption increases with the increase in temperature."