What do you mean by adsorbent and adsorbate?

Answer:

The substance adsorbed on the surface is called the adsorbate and the substance on which it is adsorbed is called adsorbent.
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Is adsorption exothermic or endothermic?

Answer:
Adsorption is always exothermic. This statement can be explained in two ways.

(i)Adsorption leads to a decrease in the residual forces on the surface of the adsorbent. This causes a decrease in the surface energy of the adsorbent. Therefore, adsorption is always exothermic.


(ii)ΔH of adsorption is always negative. When a gas is adsorbed on a solid surface, its movement is restricted leading to a decrease in the entropy of the gas i.e., ΔS is negative. Now for a process to be spontaneous, ΔG should be negative.

ΔG= ΔH-TΔS
Since ΔSis negative, ΔH has to be negative to make ΔG negative. Hence, adsorption is always exothermic.

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Define physical and chemical adsorption.

Answer:

If the adsorbate is held on the surface by weak Van der Waal’s forces, the process is called physical adsorption.

When an adsorbate is held on the surface of the adsorbent by chemical forces, it is called chemical adsorption.
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What is an adsorption isotherm and isobar?


Answer:

The variation in the amount of gas adsorbed by the adsorbent with pressure at constant temperature can be expressed by means of a curve termed as adsorption isotherm.

A plot of the amount of gas adsorbed x / m against the pressure at constant temperature is called an adsorption isotherm.


A plot of the amount adsorbed x / m versus temperature at constant pressure is called an adsorption isobar.
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What is desorption?

Answer:

The process of removing an adsorbed substance from the surface on which it is adsorbed is called desorption.
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