Which one of the following substances adsorbs hydrogen gas most strongly?

Sorption is a phenomenon where:

What is the difference between adsorbent and adsorbate?

Freshly prepared precipitate of $Fe(OH)_3$ is peptized by adding a solution of $FeCl_3$. The charge on the colloidal particles is due to the adsorption of ........

$2.0 \, g$ of $H_2$ gas is adsorbed on $2.5 \, g$ of platinum powder at $300 \, K$ and $1 \, bar$ pressure. The volume of the gas adsorbed per gram of the adsorbent is $..... \, mL$.
(Given: $R = 0.083 \, L \, bar \, K^{-1} \, mol^{-1}$)

The charge on colloidal particles is due to