Which of the following expressions describes Freundlich adsorption isotherm?

Options

A. `x//m=kP^(n)`
B. `x//m=ksqrt(P)`
C. `x//m=kP^(1//n)`
D. `x//m=P^(1-n)`

Answer

C

Explanation

Freundlich `(1909)` gave an empirical relationship between the equantity of gas adsorbed by unit mass of solid adsorbent and pressure at a particular temperature. The relationship can be expressed by the following equation
`(x)/(m)=kP^(1//n)(nge1)`
where `x` is the mass of the gas adsorbed on mass `(m)` of the adsorbent at pressure `P,K` and `n` are constant which depend on the nature of the adsorbent and the gas at a particular temperature.
The relationship is generally represented in hte from of a curve where mass of the adsorbed per gram of the adsorbent is plotted against pressure.
There curves indicate that at a fixed presuure, there is a decrease in physical adsorption with increase in temperature These curves always sem to approach saturation at high presuure. At low value of presuure, the graph is nearly straight and sloping positively:
`(x)/(m)propP^(1)` or `(x)/(m)=kP^(1)`
At high pressure, `x//m` becomes independent of the values of pressure:
`(x)/(m)propP^(@)` or `(x)/(m)=kP^(@)`
In the intermediate ranges of pressure, `x//m` will depend on `p` raised to powers between `1` and `0` or fractions. For a small range of pressure value we can write:
`(x)/(m)propP^(1//n)` or `(x)/(m)=kP^(1//n)`