Question

Adsorption of gas on a surface follows Freundlich adsorption isotherm. Plot of $\log x/m$ versus $\log P$ gives a straight line with slope equal to $0.5$, then:
($x/m$ is the mass of the gas adsorbed per gram of adsorbent)

• A. Adsorption is proportional to the square of pressure
• B. Adsorption is independent to pressure
• C. Adsorption is proportional to the pressure
• D. Adsorption is proportional to the square root of pressure

Answer 1

The correct option is D Adsorption is proportional to the square root of pressure

According to Freundlich isotherm,
$\frac{x}{m}=k{P}^{1/n}$

Taking log on both side
$\log \frac{x}{m}=\log k+\frac{1}{n}\log P$
$y=c+mx$
Here, $1/n$ represents slope $=0.5$
So $\frac{x}{m}=k{P}^{1/n}$
$\Rightarrow \frac{x}{m}\propto \sqrt{P}$
Hence, the correct option is d.