What is the role of activated charcoal in gas masks used in coal mines?

What type of phenomenon is adsorption? What type of reaction is adsorption?

$CH_4$ is adsorbed on $1 \ g$ charcoal at $0^{\circ} C$ following the Freundlich adsorption isotherm. $10.0 \ mL$ of $CH_4$ is adsorbed at $100 \ mm$ of $Hg$,whereas $15.0 \ mL$ is adsorbed at $200 \ mm$ of $Hg$. The volume of $CH_4$ adsorbed at $300 \ mm$ of $Hg$ is $10^x \ mL$. The value of $x$ is $....\times 10^{-2}$ (Nearest integer). [Use $\log_{10} 2=0.3010, \log_{10} 3=0.4771$]

Which one of the following characteristics is not correct for physical adsorption?

Distinguish between the meaning of the terms adsorption and absorption. Give one example of each.

Assertion $(A)$: The property of adsorption is shown to a greater extent by solids than liquids.
Reason $(R)$: Solids like charcoal and silica can act as good adsorbents.