Question

Which of the following is not a colloid?
A.Smoke
B.Haemoglobin
C.Latex
D.Air

Answer 1

We know that a colloid is a system of homogeneous nature in which one particle is dispersed as very fine particles in another medium known as dispersion medium. The size of particles of colloids is larger than the particles of solution.

Complete step by step answer:
The classification of colloids are done on the basis of three criteria,
1)Physical state of dispersion medium and dispersed phase
2)Kind of interaction between dispersion medium and dispersed phase
3)Particle type of dispersed phase
Now, come to the question. We have to identify the substance which is not a colloid.
Option A is smoke. Smoke is a colloidal solution of solid in gas. The dispersion medium in smoke is gas and the dispersed phase is solid.
Option B is Hemoglobin. Hemoglobin forms colloidal suspension in RBC (Red blood cell). So, it is also a colloidal solution.
Option C is Latex. Latex is also a colloidal suspension. In latex polymeric particles dispersed in water. So, water is the dispersion medium and polymeric articles are dispersed.
Option D is air. Air is a solution composed of varying particles and gases.
So, air is not a colloid.

Hence, the correct choice is option D.

Note: Considering the physical state of dispersed phase and dispersion medium, colloids are classified in eight types, solid sol, sol, aerosol, gel, emulsion and foam. ‘Solid sol’ term indicates two colloidal systems namely, solid dispersed in solid and gas dispersed in solid. ‘Aerosol’ term also indicates two colloidal systems namely, solid dispersed in gas and liquid dispersed in gas.