Question

According to Freundlich adsorption isotherm, which of the following is/are correct?

• A. $\frac{x}{m}\propto p^{1/2}$
• B. $\frac{x}{m}\propto p^1$
• C. $\frac{x}{m}\propto p^{1/n}$
• D. All the above

Answer 1

The correct option is D All the above

Freundlich gave a relation between the amount of the gas adsorbed per unit mass of the adsorbent (m) and the pressure (p). This is known as Freundlich’s adsorption isotherm.

According to Freundlich adsorption isotherm,
$\frac{x}{m}\propto p^{1/n}$ where $n\ge 1$

In these expressions, $p$ is the equilibrium pressure and $\frac{x}{m}$ is the mass of gas absorbed per unit mass of absorbent.

At low pressure, x/m is directly proportional to the pressure. This may be expressed as:

$x/m=Kp$

Where K is constant.

At high pressure, the value of x/m becomes almost constant, i.e., it does not change with the change in pressure. The relation may be expressed as:

x/m = constant

$x/m=K{p}^0$

At the intermediate range of pressure, x/m will depend upon the power of pressure which lies between 0 to 1 i.e., fraction power of pressure. This may be expressed as:

$x/m=K{p}^{1/n}$