Why is it important to have a clean surface in surface studies?

Which of the following relationships is correct regarding the Freundlich adsorption isotherm?
$(1)$ $x/m = \text{constant}$ (at high pressure)
$(2)$ $x/m = k \cdot P^{1/n}$ (at intermediate pressure)
$(3)$ $x/m = k \cdot P$ (at low pressure)

When is the term 'sorption' used?

$A$ plot of $\log (x / m)$ versus $\log (P)$ for the adsorption of a gas on a solid gives a straight line with a slope of:

According to the Langmuir adsorption isotherm,at very high pressure,the amount of gas adsorbed $x/m$ is:

What is an adsorption isotherm? Describe Freundlich adsorption isotherm.