Bredig's arc method cannot be used to prepare a colloidal solution of which of the following?

The flocculation value of $HCl$ for arsenic sulphide sol is $30 \; mmol \; L^{-1}$. If $H_{2}SO_{4}$ is used for the flocculation of arsenic sulphide,the amount,in grams,of $H_{2}SO_{4}$ in $250 \; mL$ required for the above purpose is (molecular mass of $H_{2}SO_{4} = 98 \; g/mol$)

In the precipitation of soap,which can be used instead of $NaCl$?

$10 \ mL$ of $0.5 \ M$ $NaCl$ is required to coagulate $1 \ L$ of $Sb_2S_3$ sol in $2$ hours. The flocculating value of $NaCl$ (in millimoles) is:

Identify the sequential reactions involved in the Sol-Gel process.

Identify the method of preparation of a colloidal sol from the following.