Question

The correct statement(s) about surface properties is (are):
(A) Cloud is an emulsion type of colloid in which liquid is dispersed phase and gas is dispersion medium
(B) Adsorption is accompanied by decrease in enthalpy and decrease in entropy of the system.
(C) The critical temperature of ethane and nitrogen are 563 K and 126 K , respectively. The adsorption of ethane will be more than that of nitrogen on the same amount of activated charcoal at a given temperature.
(D) Brownian motion of colloidal particles does not depend on the size of the particles but depends on viscosity of the solution.

Answer 1

As we know that, adsorption is the process of attraction of particles on the surface of solid by physically or chemically. Emulsion is the process of colloidal dispersion. As the size of the particles increases, the movement of particles becomes low.

Complete answer
Now we will see the option one by one.
A. Cloud is formed by the floating of water droplets in the air. The water vapours condense in the upper atmosphere and has less density than air so it floats into the air. So, it is liquid in gas type of sol not the emulsion.
B. Adsorption is the process of attraction of particles on the surface of the solid so when the particles get absorbed its random motion decreases and due to bonding between surface of particles, energy is released. So, we can say that adsorption is accompanied by decrease in enthalpy and decrease in entropy of the system.
C. The critical temperature is the temperature when a gas can not liquify above it at any pressure. So, more the critical temperature of the gases, more has the tendency to liquify when pressure is applied. In this way, we can say that gases are more random and when pressure is applied on them, they will absorb to a greater extent.
D. Brownian motion of colloidal particles is the zig-zag motion of the particles, small particles can move efficiently in zig-zag motion. Viscosity is the rate of flow of liquid, more the viscosity lesser will be the rate to flow. Hence, we can say that Brownian motion of colloidal particles depends on the size of the particles and viscosity of the solution.

**Therefore, the correct options are option (B) and (C).

Note: **
Brownian movement does not depend upon the nature of colloids. The reason for the Brownian movement is based on the fact that molecules of dispersion medium are due to the kinetic energy strike against the colloidal particles.