Gold number is associated with

The properties of a colloidal solution are primarily due to:

The density of gold is $19 \ g/cm^3$. If $1.9 \times 10^{-4} \ g$ of gold is dispersed in one litre of water to give a sol having spherical gold particles of radius $10 \ nm$,then the number of gold particles per $mm^3$ of the sol will be

Identify the correct statements from the following:
$(i)$ $A$ closed vessel containing $90 \%$ $CO_2$ and $10 \%$ $O_2$ is an aerosol.
$(ii)$ Milk is an emulsion.
$(iii)$ Smoke is an aerosol.
$(iv)$ Peptisation is a method of purification of colloidal solution.
$(v)$ Ultrafiltration is a method of purification of colloidal solution.

Lyophilic sols are more stable than lyophobic sols because:

Which of the following substances is not useful in forming a lyophilic sol?