Question

Powdered substances are more effective adsorbents than their crystalline form because:

a.) Adsorption is an exothermic process
b.) They become inert and do not react with the adsorbate
c.) The extent of adsorption increases with an increase in surface area of the adsorbent
d.) Adsorption is more if the size of adsorbent is small

Answer 1

Hint: Adsorption: It is a surface phenomenon of accumulation of molecules of a substance at the surface rather than the bulk of a solid or liquid is called adsorption.

Complete answer:
Adsorbate is the substance that gets adsorbed on the surface of the solid while adsorbent is the solid substance over which adsorption takes place.
Powdered substances are more effective adsorbents than their crystalline form because the surface area of the powdered substance is more and we know that physisorption is directly proportional to the surface area of the adsorbent.
In the case of a crystalline or bulk form, the surface area is less, so the molecules present on the lowest layer cannot be asserted that effectively.
Hence, we can say that powdered substances are more preferable because the substance will be distributed all over.
The correct option is ${ C }$
Additional Information:
There are several other factors which affect the rate of adsorption such as;
Nature of the gas.
The surface area of the solid.
Effect of pressure ( adsorption increases as the pressure increases).
Physisorption:- It is defined as the process in which adsorbate is held on the surface of the adsorbent by van der Waal forces.
It is a reversible process and it usually occurs at low temperatures.
Note: The possibility to make a mistake is that you may choose the option ${ A }$. As we know that adsorption is an exothermic process but here, the powdered substances are preferred due to an increase in the surface area, not because of the enthalpy.