Choose the incorrect statement pertaining to the adsorption of gas on a solid surface

Options

A. Adsorption is always exothermic
B. Physisorption may transform into chemisorption at high temperature
C. Physisorption increases with increasing temperature but chemisorption decreases with increasing temperature
D. Chemisorption is more exothermic than physisorption, however it is very slow due to higher energy of activation

Answer

To determine the incorrect statement pertaining to the adsorption of gas on a solid surface, we need to analyze the statements related to the process of adsorption.

### Step-by-Step Solution:

1. **Understanding Adsorption**:
- Adsorption is the process where gas molecules (adsorbate) adhere to the surface of a solid (adsorbent). This process can be classified into two types: physisorption and chemisorption.

2. **Physisorption**:
- Physisorption is a type of adsorption that occurs due to weak van der Waals forces. It is generally favored at low temperatures because the gas molecules can easily adhere to the surface without forming strong bonds.

3. **Chemisorption**:
- Chemisorption involves the formation of strong chemical bonds between the adsorbate and the adsorbent. This process is typically exothermic, meaning it releases energy.

4. **Analyzing the Statements**:
- **Statement 1**: "Physisorption may transfer into chemisorption at a high temperature."
- This statement is true. As temperature increases, the energy of the system may allow physisorbed molecules to undergo a transition to chemisorption.

- **Statement 2**: "Physisorption increases with increasing temperature."
- This statement is false. Physisorption is favored at low temperatures, so it does not increase with increasing temperature.

- **Statement 3**: "Chemisorption is an exothermic process."
- This statement is true. Chemisorption releases energy and is exothermic.

5. **Identifying the Incorrect Statement**:
- Based on the analysis, the incorrect statement is the second one: "Physisorption increases with increasing temperature."

### Conclusion:
The incorrect statement pertaining to the adsorption of gas on a solid surface is: **"Physisorption increases with increasing temperature."**