The correct statement$(s)$ pertaining to the adsorption of a gas on a solid surface is (are):
$(A)$ Adsorption is always exothermic.
$(B)$ Physisorption may transform into chemisorption at high temperature.
$(C)$ Physisorption increases with increasing temperature but chemisorption decreases with increasing temperature.
$(D)$ Chemisorption is more exothermic than physisorption,however it is very slow due to higher energy of activation.

In Freundlich adsorption,the amount of gas adsorbed is proportional to pressure $P$ as

Why is the adsorption of a gas on a solid exothermic?

Give a reason why a finely divided substance is more effective as an adsorbent.

In Freundlich adsorption isotherm,the value of $1/n$ is

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ Amongst $He$,$Ne$,$Ar$ and $Kr$; $1 \ g$ of activated charcoal adsorbs more of $Kr$.
Reason $R$: The critical volume $V_c \left( cm^3 \ mol^{-1} \right)$ and critical pressure $P_c \left( atm \right)$ is highest for Krypton but the compressibility factor at critical point $Z_c$ is lowest for Krypton.
In the light of the above statements,choose the correct answer from the options given below.