Which of the following statements is incorret about physisorption?

Options

A. It is a reversible process.
B. It requires less heat of adsorption .
C. It requires activation energy.
D. It takes place at low temperature

Explanation

To determine which statement is incorrect about physisorption, we will analyze the characteristics of physisorption step by step.

### Step 1: Understand Physisorption
Physisorption, also known as physical adsorption, is a process where molecules (adsorbate) adhere to a surface (adsorbent) through weak Van der Waals forces. This is distinct from chemisorption, where stronger chemical bonds are formed.

**Hint:** Physisorption involves weak interactions, unlike chemisorption which involves strong chemical bonds.

### Step 2: Characteristics of Physisorption
1. **Weak Forces of Attraction**: The primary characteristic of physisorption is that it occurs due to weak Van der Waals forces between the adsorbate and adsorbent.

**Hint:** Remember that the strength of the forces involved is a key factor in determining the nature of adsorption.

2. **Reversibility**: Physisorption is a reversible process because the weak forces can easily be broken. This means that the adsorbate can be removed from the adsorbent without significant energy input.

**Hint:** Consider how easily the adsorbate can be detached from the adsorbent when evaluating reversibility.

3. **Heat of Adsorption**: Physisorption requires less heat of adsorption compared to chemisorption. This is because the interactions are weak, and less energy is needed to overcome these forces.

**Hint:** Think about the energy changes involved in breaking weak interactions versus strong bonds.

4. **Activation Energy**: Physisorption does not require activation energy. Since there are no chemical bonds being formed or broken, the process can occur spontaneously without the need for additional energy.

**Hint:** Activation energy is typically associated with processes that involve bond formation or breaking.

5. **Temperature Dependence**: Physisorption generally occurs at low temperatures. This is because the weak forces are more effective at lower thermal energies, allowing the adsorbate to adhere to the adsorbent.

**Hint:** Consider how temperature affects the kinetic energy of molecules and their ability to adhere to surfaces.

### Step 3: Evaluate the Statements
Now, let's evaluate the given statements about physisorption:

1. **It is a reversible process** - Correct.
2. **It requires less heat of adsorption** - Correct.
3. **It requires activation energy** - Incorrect.
4. **It takes place at low temperature** - Correct.

### Conclusion
The incorrect statement about physisorption is that it "requires activation energy."

**Final Answer:** The incorrect statement is that physisorption requires activation energy.