The adsorption of a gas on a solid surface varies with pressure of the gas in which of the following manner

Fast ⟶ slow ⟶ independent of the pressure
Slow ⟶ fast ⟶ independent of the pressure
Independent of the pressure ⟶fast ⟶ slow
Independent of the pressure ⟶ slow ⟶ fast

Solution

Adsorption of a gas on solid is represented by following equilibria,Gas (Adsorbate) + solid (Adsorbent) ⇌ Gas adsorbed on solid+ Heat
Initially adsorption increases with increase in pressure at a particular temperature then got slow. After attaining equilibrium adsorption become independent of pressure.

Which of the following statements is not correct ?

Physical adsorption is due to van der Waal’s forces
Chemical adsorption first decreases with increase in temperature.
Physical adsorption is reversible
Adsorption energy for a chemical adsorption is generally greater than that of physical adsorption

Which among the following statements are correct with respect to adsorption of gases on a solid?
(i)The extent of adsorption is equal to kpⁿ according to Freundlich isotherm
(ii)The extent of adsorption is equal to to kp^1/n according to Freundlich isotherm
(iii)The extent of adsorption is equal to (1+bp)/ap according to Langmuir isotherm
(iv)At low pressure x/m is directly proportional to the pressure

(i) and (iii)
(i) and (iv)
(ii) and (iii)
(ii) and (iv)

Solution

In physical adsorption, gas molecules are bound on the solid surface by

chemical forces
electrostatic forces
gravitational forces
van der Waal’s forces

Solution

In physisorption, gas molecules are held on the solid surface by weak van der Waal’s forces.

Adsorption due to strong chemical forces is called

Chemisorption
Physisorption
Reversible adsorption
Both (b) and (c)

Solution

Chemisorption involves strong chemical forces.

How many layers are adsorbed in chemical adsorption ?

One
Two
Many
Zero

Solution

Chemical adsorption involves formation of monolayer.

Pick out the statement which is not relevant in the discussion of colloids:

Sodium aluminium silicate is used in the softening of hard water
Potash alum is used in shaving rounds and as a styptic in medicine
Artificial rain is caused by throwing electrified sand on the clouds from an aeroplane
Deltas are formed at a place where the river pours its water into the sea

Solution

This statement is not relevant in discussion of colloids as softening of hard water involves removal of salts that cause hardness of water i.e., salts of Ca²⁺ and Mg²⁺

In Langmuir’s model of adsorption of a gas on a solid surface

the mass of gas striking a given area of surface is proportional to the pressure of the gas
the mass of gas striking a given area of surface is independent of the pressure of the gas
the rate of dissociation of adsorbed molecules from the surface does not depend on the surface covered
the adsorption at a single site on the surface may involve multiple molecules at the same time

Solution

According to Langmuir's model of adsorption of a gas on a solid surface the mass of gas adsorbed(x)per gram of the adsorbent (m) is directly proportional to the pressure of the gas (p) at constant temperature.

The dispersed phase, dispersion medium and nature of colloidal solution(lyophilic or lyophobic) of ‘gold sol’respectively, are

solid, solid, lyophobic
liquid, liquid, lyophobic
solid, liquid, lyophobic
soild, liquid, lyophilic

Solution

In case of gold sol, we have
Dispersed phase – solid.
Dispersion medium – liquid
Gold sol is lyophobic colloid. i.e., (c) is correct

What is the name given to a phenomenon in which both adsorption and absorption take place?

Chemisorption
Physiosorption
Desorption
Sorption

Solution

Sorption : Absorption and adsorption occur together.Absorption : Particles of gas or liquid get uniformly distributed throughout the body of solid and the force of attraction between them is weak vander waal’s force of attraction or by some bond formation.
Adsorption ⟶ Physical adsorption (vander waal’s force of a attraction)
Chemical adsorption (bond formation between adsobed and adsorbate molecules)

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