Which of the following statements is correct regarding physical adsorption?
1
The forces of attraction between the adsorbent and adsorbate are of van der Waals type (weak forces).
2
Physisorption occurs at high temperatures and involves chemical bonds between adsorbate and adsorbent.
3
Physisorption is usually irreversible and specific in nature.
4
The enthalpy of adsorption is high, typically between 80 to 420 kJ mol⁻¹.