Question

Which of the following are correct about Langmuir adsorption isotherm at a very high pressure?

• A. It is valid for chemisorption.
• B. $\frac{x}{m}=\frac{a}{b}$
• C. $ln\frac{x}{m}=\frac{\Delta S^{\circ }}{R}-\frac{\Delta H^{\circ }}{RT}$
• D. At very high pressure, rate of adsorption $>$ rate of desorption.

Answer 1

Answer: (A), (B), (C)

The correct options are
A It is valid for chemisorption.
B $\frac{x}{m}=\frac{a}{b}$
C $ln\frac{x}{m}=\frac{\Delta S^{\circ }}{R}-\frac{\Delta H^{\circ }}{RT}$

At very high pressure, rate of adsorption $=$ rate of desorption

Therefore, $\frac{x}{m}=\frac{a}{b}=K_{eq}$ or equilibrium is attained.
$\Delta G^{\circ }=-2.303RTlog\frac{x}{m}$
or $\Delta H^{\circ }-T\Delta S^{\circ }=-2.303RTlog\frac{x}{m}$