Which type of adsorption leads to the formation of a multimolecular layer?

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

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 ........

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 ........ $L$. $(N_A = 6 \times 10^{23})$

In the process of adsorption,which of the following values is less than zero?

According to the Langmuir adsorption isotherm,which of the following plots is a straight line?