Question

Which of the following electrolytes will have maximum flocculation value for $Fe{\left( {OH} \right)_3}$ sol?
A.NaCl
B. $N{a_2}S$
C. ${\left( {N{H_4}} \right)_3}P{O_4}$
D. ${K_2}S{O_4}$

Answer 1

A colloid is a mixture of particles of nanometers in diameter, also called colloidal dispersions because the substances remain dispersed and do not settle at the bottom. They may either dissolve macromolecules or may represent a separate phase, such as powders, emulsions, aerosols, etc.

Complete step by step answer:
Sol is a colloid in which the dispersed phase is solid and the dispersion medium is liquid. Colloids can be understood as an aggregate of very fine tiny particles dispersed in a continuous medium. Sol can be negatively charged or positively charged.
The minimum amount of electrolyte is required to coagulate the sol is the flocculation value of electrolyte. The higher the value of flocculation lower will be the coagulation power of that electrolyte.
In this case, $Fe{\left( {OH} \right)_3}$ is a positively charged sol. Now, according to the definition of flocculation value, the maximum flocculation value for $Fe{\left( {OH} \right)_3}$ sol is for NaCl. Because $C{l^ - }$ ion has the lowest negative charge among all the given options.

So, the correct option is A.

Additional information:
Colloids are majorly classified as:
1.Sol is a colloidal suspension with solid particles in a liquid which is a dispersion medium.
2.Foam is formed when gas particles get trapped in either solid or liquid.
3.The emulsion is between two liquids i.e. dispersion phase and dispersion medium both are liquid.
4.Aerosol has small particles of liquid or solid dispersed in a gas or air which is the dispersion medium here.
5.Sol is a colloidal system of solid dispersed in a liquid medium.

Note: The interchange of the dispersion phase and the dispersion medium changes the colloidal system. For example, in the case of the colloidal system of liquid dispersed in a solid dispersion medium, it is referred to as gel.