Surface Chemistry — Chemistry STD 12 Science — Question

 

1.

The forces of attraction between adsorbent and adsorbate are of Van der Waals type (weak forces).

The forces of attraction between adsorbent and absorbate are of a chemical nature (strong forces).

2.

This predominates at low temperatures.

This usually occurs at high temperatures.

3.

Almost all gases show this type of adsorption at low temperatures.

It is highly specific in nature.

4.

The heat of adsorption is low and has a value of about $40$ kJ per mole or less.

The heat of adsorption is high and has a value of the order of $80$ to $420$kJ per mole.

5.

This type of adsorption attains equilibrium very rapidly on changing the temperature and pressure of the system.

This type of adsorption is relatively slower.

6.

This is usually irreversible in nature. For example, $O_2$ adsorbed on charcoal, when adsorbed also releases $CO$ and $CO_2.$

7.

The activation energy involved in this adsorption is small and is often less than $5$ kJ. It is for this reason, this is even attained at low temperatures.

The activation energy involved in this adsorption is high. It is for this reason, it is attained only at high temperatures.

8.

Adsorption in this case is often multilayer.

Adsorption in this case in monolayer.