Which one of the following is/are correct statement for 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 statements about physisorption are correct, let's analyze each option based on the properties of physisorption.

### Step-by-Step Solution:

1. **Understanding Physisorption**:
- Physisorption, also known as physical adsorption, involves weak Van der Waals forces between the adsorbate (the substance being adsorbed) and the adsorbent (the surface on which adsorption occurs).
- It is characterized by temporary adsorption and is a reversible process.

2. **Analyzing the Properties**:
- **Reversible Process**: Physisorption is indeed a reversible process, meaning that the adsorbed molecules can easily detach from the surface.
- **Heat of Adsorption**: The heat of adsorption (ΔH) for physisorption is low, typically in the range of 20 to 40 kJ/mol, indicating that it requires less energy.
- **Activation Energy**: Physisorption does not require activation energy, which distinguishes it from chemisorption, where a significant amount of energy is needed to break bonds.
- **Temperature Dependence**: Physisorption occurs more readily at lower temperatures, and its efficiency decreases as the temperature increases.

3. **Evaluating Each Option**:
- **Option 1**: "It is a reversible process."
- **Correct**: Physisorption is reversible.
- **Option 2**: "It requires less heat of adsorption."
- **Correct**: The heat of adsorption is low (20 to 40 kJ/mol).
- **Option 3**: "It requires activation energy."
- **Incorrect**: Physisorption does not require activation energy.
- **Option 4**: "It takes place at low temperature."
- **Correct**: Physisorption is favored at low temperatures.

### Conclusion:
The correct statements regarding physisorption are:
- Option 1: Correct
- Option 2: Correct
- Option 3: Incorrect
- Option 4: Correct

### Final Answer:
Options 1, 2, and 4 are correct statements for physisorption.

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