Question

For adsorption of a gas on solid surface, the plot of log $\frac{x}{m}$ vs log $P$ is linear with slope equal to :

• A. $K$
• B. $logK$
• C. $\frac{1}{nK}$
• D. $\frac{1}{n}$ ($n$ being integer)

Answer 1

The correct option is D $\frac{1}{n}$ ($n$ being integer)

For adsorption of a gas on solid surface, the plots of log $\frac{x}{m}$ vs log $P$ is linear with a slope equal to $\frac{1}{n}$ ( $n$ being integer). As the temperature increases, the constants change to reflect the empirical observation that the quantity adsorbed rises more slowly and higher pressures are required to saturate the surface. Higher the $\frac{1}{n}$ value, more favorable is the adsorption.

$log\frac{x}{m}=logK+\frac{1}{n}logP$

This is the Freundlich isotherm. Thus, slope $=\frac{1}{n}$