Question

Which of the following is / are correct statements ?
(This question has multiple correct options )
A.Hardy Schulz rule is related to coagulation
B.Brownian movement and Tyndall effect are shown by colloids
C.When liquid is dispersed in liquid , it is called gel
D.Gold number is a measure of protective power of lyophilic colloid

Answer 1

A colloid is a heterogeneous system in which one substance is dispersed as fine particles in another substance called dispersion medium .

Complete step by step answer:
According to Hardy Schulz law when excess electrolyte is added to colloidal solution having charge opposite to that of sol then coagulation will take place due to neutralization of charges , greater the charge on the electrolyte more is the coagulation . Hence we can say that Hardy Schulz law is related to coagulation and option A is correct .
When colloidal particles are observed under ultra - microscope then it is observed that they are moving in zig-zag fashion . This movement is termed the Brownian movement .
Also the dimensions of colloidal particles are such that they can scatter light . This is called the Tyndall effect .
Hence option B is correct .
Gel is a colloid in which liquid is dispersed in solid , like in jelly , butter and cheese .
Hence option C is not correct .
Gold number is the amount of a protective colloid ( in milligrams ) which is just sufficient to prevent coagulation of 10 ml of a standard gold sol when 1 ml of $10\% NaCl$ solution is added to it .
It is used for measuring the protective power of lyophilic colloids .
Hence option D is also correct .

Note:
The presence of a small quantity of electrolyte is essential for the stability of the sol .
To observe Tyndall effect certain conditions should be met : Diameter of dispersed colloidal particles should not be much smaller than the wavelength of light and the refractive index of dispersed phase and dispersion medium should differ greatly in magnitude .