This equation represents the preparation of gold sol: $2 AuCl_3 + 3 HCHO + 3 H_2 O \rightarrow 2 Au + 3 HCOOH + 6 HCl$. What type of reaction is this?

The coagulating power of an ion for a colloidal solution depends on which of the following?

Among the following methods:
$(i)$ Addition of an electrolyte
$(ii)$ Electrophoresis
$(iii)$ Addition of a protective colloid
$(iv)$ Addition of an oppositely charged sol
the coagulation of a lyophobic sol can be carried out by:

Statement $I:$ For colloidal particles,the values of colligative properties are of small order as compared to values shown by true solutions at the same concentration.
Statement $II:$ For colloidal particles,the potential difference between the fixed layer and the diffused layer of opposite charges is called the electrokinetic potential or zeta potential.
In the light of the above statements,choose the correct answer from the options given below.

The gold numbers of protective colloids $A, B, C,$ and $D$ are $0.50, 0.01, 0.10,$ and $0.005$ respectively. The correct order of their protective power is:

An emulsifier is a substance which