Question

The cause of Brownian movement which is not shown by true solutions or suspensions is due to:

(A) Unbalanced bombardment of particles by molecules of the dispersion medium
(B) Attractive forces between dispersed phase and dispersion medium
(C) Larger size of the particles due to which they keep colliding and settling down
(D) Conversion currents formed in the sol.

Answer 1

Hint: Particle size in solutions and suspensions are very small compared to particle sizes of colloids. Brownian movement is a random movement of particles that occur due to collision of particles.

Complete step by step solution:
- Brownian movement is the random movement of particles in the fluid which move in a zig-zag manner and the main cause of this type of movement is the collision between them and fluid molecules.
- Now these collisions are not linear and are completely random, so this type of collisions are seen in the colloidal solutions.
- Now, the particle size in true solutions is very small and this movement is not seen because collisions do not occur. Same thing is with suspensions.
- So, true solutions or suspensions do not involve unbalanced bombardment of particles by molecules of the dispersion medium, therefore they do not show brownian motion.

So, correct answer is (A) Unbalanced bombardment of particles by molecules of the dispersion medium.

Additional Information:
- This effect was first observed by british botanist Robert brown.
- Brownian motion is independent of the nature of the colloid but it depends upon the size of the particles and viscosity of the fluid. The brownian motion is faster as the size of particles are smaller and viscosity of the fluid is lesser.

Note: Do not assume that as particles are colliding ,then they will coagulate and settle down, in fact brownian movement has a stirring movement and this effect does not allow the particles to settle down in colloidal solutions. Always remember that brownian motion is dependent on the size of particle and viscosity of fluid.