Freundlich's adsorption isotherm for adsorption of gases in the form of an equation
\(\frac { x }{ m } ={ kp }^{ 1/n }\)
where, m = mass of adsorbent, x = mass of the gas adsorbed on mass m,
p = pressure and k,n = constants
ii) Lyophilic sols are reversible sols. These are quite stable and cannot be coagulated.
(iii) Associated colloid Soap solution, detergent Multimolecular colloid Sulphur sol, gold sol.

(i) Lyophilic sol The colloidal solution in which the particles of the dispersed phase have a great affinity for the dispersion medium is called lyophilic sol. e.g. gum, geletin. starch etc.
Lyophobic sol The colloidal solution in which there is no affinity between particles of the dispersed phase and the dispersion medium is called lyophobic sol. Lyophobic sols need, stabilising agents for their preservation.
(ii) Solution It contains small solute particles dispersed throughout the solvent. The particle size is less than 1 nm
Colloid It contain particles of intermediate size. It is a heterogeneous solution. The particles of colloid have diameters between 1 to 1000 nm.
(ii) Homogeneous catalysis It is the phenomenon in which reactants and catalyst are present in the same phase
\(2{ SO }_{ 2 }(g)+{ O }_{ 2 }(g)\overset { NO(g) }{ \longrightarrow } 2{ SO }_{ 3 }(g)\)
Heterogeneous catalysis It is the phenomenon in which reactants and catalyst are present in the different phase
\(2{ SO }_{ 2 }(g)+{ O }_{ 2 }(g)\overset { Pt(s) }{ \underset { Oxidation }{ \longrightarrow } } 2{ SO }_{ 3 }(g)\).

The process of breaking an emulsion into its constituent liquids is called demulsification. Freezing, boiling, centrifugation, electrostatic precipitation or adding dehydrating agent leads to demulsification, e.g. lemon juice demulsifies milk.

(a) Same substances like soap can act as crystalloids in low concentration, whereas in high concentration, it forms a colloidal solution.
(b) Spraying salts like AgI over clouds makes some clouds +ve, whereas other -ve. When positively and negatively charged clouds come close to each other, they cause artificial rain.
(c) It is due to scattering of light by colloidal particles.

Surface area of charcoal adsobed by each molecule = \(\frac { 3.01\times { 10 }^{ 2 }{ m }^{ 2 } }{ 6.02\times { 10 }^{ 20 } } =5\times { 10 }^{ -19 }{ m }^{ 2 }\)

(i) Soaps work due to the formation of micelles. But the formation of micelles takes place at a minimum temperature called 'Kraft temperature'. This temperature is reached in luke warm water.
(ii) Be humble to accept a scientific fact from a elder person.

(i) Finely divided nickel is used as catalyst in hydrogenation.
(ii) No, we should use vegetable oil instead of vegetable ghee as it is partly saturated, may lead to formation of cholesterol.
(iii) Nickel gets mixed with vegetable ghee. It is harmful for our body as it is found to be carcinogenic (cancer causing).
(iv) It is because these led to the formation of excess of acid, which leads to hyperacidity, indigestion and stomach disorders.
(v) These are basic in nature and thus can induce more secretion of hydrochloric acid in gastric juice, that is why, these should be avoided as far as possible.

(i) It absorbs poisonous gases to large extent and not oxygen which is used for breathing.
(ii) It absorbs the undesirable colours from aqueous solution of sugar, we get colourless sugar.
(iii) Silica gel absorbs water molecules on its surface which may spoil the equipment.
(iv) Whenever there is excess of carbon monoxide gas, the colour of flame becomes blue and coal mine workers are asked to come out because carbon monoxide gas may lead to death.

(i) Dust and smoke coming out of chimney can be controlled by installing cottrell smoke precipitator. 
(ii) Cottrell precipitator consists of two metal discs charged to a high electrical potential. The charge on colloidal dust and carbon particles of smoke is neutralised and they get precipitated while free gases escape out of chimney. 
(iii) The knowledge of cottrell precipitator and management of dust and carbon particles of smoke can help us to clean our environment and make it healthier. Eco-friendliness and self-awareness are values associated with it.

(i) Blood is a colloidal solution of albuminoid substance. The styptic action (blood stopping action) of alum is due to coagulation of blood forming a clot which stops further bleeding.
(ii) Values associated with Meera's decision are:
(a) Friendship
(b) Keen observation
(c) Applying knowledge of chemistry to daily life
(d) Responsibility
(e) Love and care.

(a) Electrophoresis. The phenomenon of movement of colloidal particles under an applied the electric field is called electrophoresis. This helps to know the presence of charge on the sol particles and its nature whether positive or negative. In' this experiment, the colloidal particles move towards positive or negative electrodes depending upon their charge under the influence of electrical field. If the particles accumulate near the negative electrode, the charge on the particles is positive. On the other hand, if the sol particles accumulate near the positive electrode, the charge on the particles is negative. The apparatus consists of U tube with two platinum electrodes in each limb. Take a sol of AS₂S₃ in the U-tube. The intensity of the color of the sol in both the arms is same. Now, pass the current through the soL After some time, it

electrode became intense than the initial color. This indicates that the AS₂S₃particles have accumulated near the positive electrode. Therefore, the particles of AS₂S₃ are negatively charged and they move towards oppositely charged (positive) electrode and get accumulated there. Similarly, when an electric current is passed through positively charged Fe(OH)₃sol, it is observed that they move towards negatively charged electrode and get accumulated there. Thus, by observing the direction of movement of the colloidal particles, the sign of the charge carried by the particles can be determined.
(ii) Coagulation. The phenomenon of ." precipitation of a colloidal solution by the addition of an excess of an electrolyte is called coagulation or Occultation. The coagulation capacity of different electrolytes depends upon the valency of the active ion or called flocculating ion. It is the ion carrying a charge opposite to the charge on the colloidal particles. According to Hardy Schulz law, greater the valency of the active ion or flocculating ion, greater will be its coagulating power. Thus, to coagulate negative sol of AS₂S_3. the coagulating power of different actions has been found to decrease in the order as:
Al₃+> Mg₂+>Na+
Similarly, to coagulate a positive sol., such as Fe(OH)₃ the coagulating power of different anions has been found to decrease in the order:
[Fe (CN)]⟶ PO:⟶ SO⟶ CI^-
(iii) Dialysis.The method used to separate the impurities from the colloidal solution is called dialysis. Its principle is based on the fact that colloidal particles cannot pass through a parchment or cellophane membrane while the ions of the electrolyte can pass through it. The colloidal solution is taken in It bag made of cellophane or parchment. The bag is suspended in fresh water. The impurities slowly diffuse out of the bag leaving behind the pure colloidal solution. Dialysis can be used for removing HCI from the ferric hydroxide sol

The ordinary process of dialysis is slow. To increase the process of purification, the dialysis is carried out by applying an electric field. This process is called electrodialysis.
(iv) 'Tyndall effect. When a strong beam of light is passed through a true solution placed in a beaker, in a dark room, the path of the light does not become visible as shown in However, if the light is passed through a sol, placed in the same room, the path of the light becomes visible when viewed from a direction at right angle to that of the incident beam.

This phenomenon was studied for the first time by Tyndall and therefore it is called Tyndall effect. The cause to Tyndall effect is the scattering of light by colloidal particles i.e., these particles first absorb the incident ligand then a part of it gets scattered by them. Since the intensity of the scattered light is at a right angle to the plane of the incident light, the path becomes visible only when seen in that direction. The particles in true solution are too small in size to cause any scattering i.e., the Tyndall effect is not noticed in true solutions.

(i) In TLC
(ii) As adsorption incicators
(iii) In separation of inert gases.