The correct statement for both the processes of physisorption and chemisorption is

Adsorption of gases on a solid surface is generally exothermic because

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: In expensive scientific instruments,silica gel is kept in watch-glasses or in semipermeable membrane bags.
Reason $(R)$: Silica gel adsorbs moisture from air via adsorption,thus protects the instrument from water corrosion (rusting) and/or prevents malfunctioning.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following is zero during the process of adsorption?

Which of the following forces is responsible for physisorption?

The charge of $As_2S_3$ sol is due to the adsorption of