Question

Which equation of Langmuir adsorption isotherm will apply at high pressure?

• A. $\frac{x}{m}=\frac{b}{a}$
• B. $\frac{x}{m}=\frac{1}{a.p}$
• C. $\frac{x}{m}=a.p$
• D. $\frac{x}{m}=\frac{a}{b}$

Answer 1

The correct option is D $\frac{x}{m}=\frac{a}{b}$

Langmuir isotherm:

$\frac{x}{m}=\frac{ap}{1+bp}$

where $x$ is the mass of the adsorbate and $m$ is the mass of the adsorbent at pressure $p$. $a,b$ are the Langmuir parameters

At high pressure , $bp>>1$, thus $1+bp\approx bp$

and $\frac{x}{m}=\frac{ap}{bp}$

$\frac{x}{m}=\frac{a}{b}$

option D is correct