Question

Which of the following statements regarding the physical adsorption of a gas on surface of solid is not correct?

(a) On increasing temperature, adsorption increases continuously

(b) Enthalpy changes are negative

(c) Adsorption is specific

(d) It is reversible in nature

I got this question by my school teacher while I was bunking the class.

This intriguing question comes from Adsorption topic in section Unit Operations of Bioprocess Engineering

Answer 1

The correct answer is (a) On increasing temperature, adsorption increases continuously

To explain I would say: Physisorption is exothermic in nature. Therefore according to le chateliars principle, it occurs readily at low temperature and decreases with increase in temperature. Bond between adsorbent i.e. surface and adsorbate like gases are weak so when temperature is increasing the bond get break easily and adsorption of adsorbate get stop so rate will decrease on increasing temperature.