Question

Chemisorption :

• A. increases with temperature
• B. decreases with temperature
• C. remains unaffected by change of temperature
• D. first increases and then decreases with temperature

Answer 1

Answer: (D)

first increases and then decreases with temperature

Chemisorption or Chemical Adsorption: If the chemical forces hold the gas molecules to the surface of the adsorbent, the adsorption is known as chemisorption. In this case, the adsorbate undergoes a strong chemical interaction with the unsaturated surface and gives rise to a high heat of adsorption, usually of the order of $400$ kJ per mole.

Chemisorption is often characterised by taking place at elevated temperatures and is often an activated process.

It may be dissociative, non- dissociative or reactive in nature.

Generally, chemisorption occurs at high temperatures but certain examples are known in which it occurs at low temperature. Chemisorption increases at first and then falls off with rising temperature because of its exothermic nature.