Identify the correct statements from the following.
$(i)$ In the oxidation of oxalic acid with $KMnO_4$ in acid medium,$Mn^{2+}$ acts as an autocatalyst.
$(ii)$ $CdS$ colloidal solution can be precipitated by the addition of $Cl^{-}$ ions.
$(iii)$ The gold numbers of three protective colloids $(A, B, C)$ are $0.03$,$25$,and $0.25$ respectively. Their protective power follows the order $A > C > B$.
$(iv)$ Physisorption is an irreversible process.

The correct statement$(s)$ about surface properties is(are):
$[A]$ Adsorption is accompanied by decrease in enthalpy and decrease in entropy of the system.
$[B]$ The critical temperatures of ethane and nitrogen are $563 \ K$ and $126 \ K$,respectively. The adsorption of ethane will be more than that of nitrogen on the same amount of activated charcoal at a given temperature.
$[C]$ Cloud is an emulsion type of colloid in which liquid is dispersed phase and gas is dispersion medium.
$[D]$ Brownian motion of colloidal particles does not depend on the size of the particles but depends on the viscosity of the solution.

The process of setting of cement is an ...... process.

Which of the following statements are not true?

Which of the following are not completely surface phenomena?

$0.27 \ g$ of a long chain fatty acid was dissolved in $100 \ cm^3$ of hexane. $10 \ mL$ of this solution was added dropwise to the surface of water in a round watch glass. Hexane evaporates and a monolayer is formed. The distance from edge to centre of the watch glass is $10 \ cm$. What is the height of the monolayer? [Density of fatty acid $= 0.9 \ g \ cm^{-3}, \pi = 3$]