The nature of charge on resulting colloidal particles when $FeCl_3$ is added to excess of hot water is:

The apparatus used for the precipitation of carbon particles from smoke is known as.............

$X$ is a protecting colloid. The following data is obtained for preventing the coagulation of $10 \ mL$ of gold sol to which $1 \ mL$ of $10 \% NaCl$ is added. What is the gold number of '$X$'?

Expt. No.	Weight of $X$ (in $mg$) added to gold sol	Coagulation
$1$	$24$	Not prevented
$2$	$23$	Not prevented
$3$	$26$	prevented
$4$	$27$	prevented
$5$	$25$	prevented

Match column $I$ (process) with column $II$ (application).

Column $I$	Column $II$
$A$. Dialysis	$a$. Cleansing action of soap
$B$. Peptization	$b$. Coagulation
$C$. Emulsification	$c$. Colloidal solution preparation
$D$. Electrophoresis	$d$. Purification of colloidal solution

Gold numbers of some colloids are: Gelatin $0.005-0.01$,Gum arabic: $0.15-0.25$; Oleate: $0.04-1.0$; Starch: $15-25$. Which among these is a better protective colloid?

Which of the following is/are not an example of $Gel$?