Point out the false statement.

The blue color of the sky is due to $.....$.

Identify the option having the correct set of True $(T)$ or False $(F)$ statements with respect to colloidal solutions:
$(I)$ Lyophobic colloids are heavily solvated by the dispersion medium.
$(II)$ Multimolecular colloids are usually lyophilic.
$(III)$ Surface tension of a starch aqua sol will be lesser than that of water.
$(IV)$ Blood gets coagulated by the addition of $NaCl$.

On addition of $1 \ mL$ of $10 \%$ $NaCl$ to $10 \ mL$ gold sol in the presence of $0.038 \ g$ of starch the coagulation is just prevented. Then the value of gold number of starch is

Among the following electrolytes,which is the most effective coagulating agent for $Fe(OH)_3$ sol?

Which type of sol is argyrol? What are the uses of argyrol?