Question

Why chemisorption requires high activation energy?

Answer 1

Answer:

Chemisorption is a type of adsorption in which substances are adsorbed on the surface of the adsorbent.

Now, you should remember that adsorption is a surface phenomenon.

This means that the adsorbates are not taken into the bulk of the adsorbent.

Now chemisorption as the name suggests requires high activation energy because of the following reason :

1. In chemisorption, the adsorbate forms reversible covalent and even non - covalent bonds with the adsorbent.

2. Formation of such covalent, electrostatic bonds or weak interactions like H - Bonding or hydrophobic bonds require chemical reactions to occur.

3. As per Michaelis - Menten kinetics, these reactions do require a high activation energy to form a transition state.

4. Activation energy is in the range of

80 - 240 joules.

But in physisorption, such high activation energy is not needed as bond formation doesn't take place.

Answer 2

AnSwEr:

$\longrightarrow$Because chemisorption involves a high activation energy. so, it first increases and then decreases with increase in temperature.

$\longrightarrow$The initial increase is due to the heat supplied which act as activation energy required in chemisorption. But later it decreases due to exothermic nature of adsorption at euilibrium.