Surface Chemistry - Result Question 28

####29. When $O _2$ is adsorbed on a metallic surface, electron transfer occurs from the metal to $O _2$. The true statement(s) regarding this adsorption is (are)

(2015 Adv.)

(a) $O _2$ is physisorbed

(b) heat is released

(c) occupancy of $\pi^{*} 2 p$ of $O _2$ is increased

(d) bond length of $O _2$ is increased

Show Answer

Answer:

Correct Answer: 29. (c)

Solution:

  1. Since, adsorption involves electron transfer from metal to $O _2$, it is chemical adsorption not physical adsorption, hence $(a)$ is incorrect. Adsorption is spontaneous which involves some bonding between adsorbent and adsorbate, hence exothermic. The last occupied molecular orbital in $O _2$ is $\pi^{} 2 p$. Hence, electron transfer from metal to oxygen will increase occupancy of $\pi^{} 2 p$ molecular orbitals. Also increase in occupancy of $\pi^{*} 2 p$ orbitals will decrease bond order and hence increase bond length of $O _2$.


NCERT Chapter Video Solution

Dual Pane