Question

The adsorption of a gas, on a solid surface, varies with pressure of the gas in which of the following manner?
A. Slow, fast independent of the pressure
B. Fast slow independent of the pressure
C. Independent of the pressure slow fast
D. Independent of the pressure fast slow

Answer 1

Hint: The adsorption of a gas on a solid surface depends on the pressure of the gas. The variation of pressure with adsorption does not follow a regular trend. The variation of adsorption with pressure follows Freundlich adsorption isotherm. It is the variation in the amount of gas absorbed by the adsorbent with pressure at a constant temperature.

Complete Step by Step Solution:
Freundlich adsorption isotherm provided an empirical relation between the amount of gas adsorbed by a solid adsorbent at a pressure and at a particular temperature. It is expressed as follows:
$\frac{x}{m}=k.{{P}^{\frac{1}{n}}}$

Here the term $x$ is the mass of the gas adsorbed. Here $m$ is the mass of the adsorbent at pressure $P$. $k,n$ are the constants that depend on the nature of the adsorbent and the gas at a given temperature.

Thus from the above relation of Freundlich adsorption isotherm we can say that isotherm adsorption is proportional to pressure \[P\] as ${{P}^{\frac{1}{n}}}$. Thus the extent of adsorption increases with pressure but at intermediate pressure it increases slowly with pressure and at high pressure it is independent of pressure.
Thus the correct option is B.

Note: The Freundlich adsorption isotherm provided a relationship between the amount of gas adsorbed in a unit mass of solid adsorbent. This Freundlich isotherm gives us idea about the change in extent of adsorption with pressure.