Question

Which one of the following characteristics is not correct for physical adsorption?
A. Adsorption increases with increase in temperature
B. Adsorption is spontaneous
C. Both enthalpy and entropy of adsorption are negative
D. Adsorption on solids is reversible

Answer 1

Hint: Physical adsorption is a spontaneous process that means it takes place without external energy. It is inversely proportional to temperature and is reversible in nature.

Complete Step by Step Solution:
In the method of physical adsorption, the adsorption takes place between the adsorbate and adsorbent due to weak hydrogen bonding or Van Der Waals force.
The properties of physical adsorption are as follows-
1. It has weak forces like vander waals force or hydrogen bonding between adsorbate and adsorbent.
 2. Physical adsorption is reversible in nature.
3. Physical adsorption depends on the surface area of the adsorbent because as the surface area of the adsorbent will increase, physical adsorption additionally will increase.
4. Physical adsorption is the slowest process.
5. It is not independent of temperature. It increases with a decrease in temperature.
6. It is highly specific.
7. It is spontaneous and has negative enthalpy and entropy.
Thus the correct option is A.

Note: Physical adsorption is inversely proportional to the temperature due to physical bond vibration. But if the bond is strong then a higher amount of heat is required to break the bond between adsorbate and adsorbent.