For a linear plot of log (x/m) versus log p in a Freundlich adsorption isotherm

For a linear plot of log (x/m) versus log p in a Freundlich adsorption isotherm, which of the following statements is correct ? (k and n are constants)

  1. 1/n appears as the intercept.
  2. Only 1/n appears as the slope.
  3. log (1/n) appears as the intercept.
  4. Both k and 1/n appear in the slope term.

Solution

Freundlich gave an empirical mathematical relationship between the extent of adsorption x/m and the equilibrium pressure (p) of the gas as:

\( \dfrac{x}{m} = kp^{1/n} \), where n > 1

On taking logarithm of the above equation,

\( \log\dfrac{x}{m}=\log k + \dfrac{1}{n}\log p \)

This is an equation of a straight line and a plot of log x/m against log p is a straight line with slope 1/n. Intercept is log k.

 

The correct option is B.