In the adsorption of oxalic acid on activated charcoal,the activated charcoal is known as:

Which forces are involved in physical adsorption?

Which one of the following gives a straight line for Freundlich adsorption isotherm?

$A$ mixture of substances $A, B, C, D$ is subjected to column chromatography. The degree of adsorption is in the order of $D > B > C > A$. The column is eluted with a suitable solvent. Identify the correct statement with respect to the separation of the mixture.

The surface area of $1 \, g$ of activated charcoal is $1000 \, m^2$. Assuming complete coverage and unimolecular adsorption,if the radius of an ammonia molecule is $10^{-8} \, cm$,then the volume of ammonia adsorbed at $STP$ on $44/7 \, g$ of carbon will be ........ $L$. $(N_A = 6 \times 10^{23})$

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: