Q13 / 180 · KCET 2016 · Chemistry
Which of the following statements is incorrect w.r.t. Physisorption ?
- AThe forces involved are van der Waal's forces,
- BMore easily liquifiable gases are adsorbed easily.
- CUnder high pressure it results into Multi-molecular layer on adsorbent surface
- Correct answerD\( \Delta H_{\text {adsorption }} \) is low and \( +V e \)
Solution
Physisorption is an exothermic process but, its enthalpy ofadsorption is low, because attractive forces between
adsorbent and the adsorbate molecules are weak (i.e., van der Waals forces) and therefore, molar enthalpy ( \( \Delta \mathrm{H} \) ) of
adsorption is low and is of the order of \( 20-40 \mathrm{~kJ} \mathrm{~mol}^{-1} \). Maximum of gas is adsorbed when pressure is increased as
the volume of gas decreases. The gases which are easily liquefied are adsorbed readily, because van der Waals forces
are stronger near the critical temperature.
adsorbent and the adsorbate molecules are weak (i.e., van der Waals forces) and therefore, molar enthalpy ( \( \Delta \mathrm{H} \) ) of
adsorption is low and is of the order of \( 20-40 \mathrm{~kJ} \mathrm{~mol}^{-1} \). Maximum of gas is adsorbed when pressure is increased as
the volume of gas decreases. The gases which are easily liquefied are adsorbed readily, because van der Waals forces
are stronger near the critical temperature.
Hence, the correct answer is option: 'D'.