coagulating power ∝ 1/coagulation value

Emulsion-Dispersed phase
Dispersion meduun -liquid

At the time of setting, the sun is at the horizon The light emitted by the sun has to travel a longer distance through the atmosphere. As a result, blue part of the light is scattered away by the dust particles in the atmosphere. Hence, the red part is visible.

(i) When a strong beam of light is passed through a sol, the path of light is illuminated by the scattering of light by colloidal particles.
(ii) The phenomenon of the scattering of light by the sol particles is called Tyn all effect.

(i) In this method, the colloidal solution is taken in a bag made up of semipermeable membrane.
(ii) It is suspended in a trough of flowing water, the electrolytes diffuse out of the membrane and they are carried away by II water.

The action of catalyst is explained as follows
CH₃Cl + AlCl₃  → [CH₃ ]⁺[AlCl₄]^-
It is an intermediate.
C₆H₆ + [CH₃⁺][AlCl₄]^- → C₆H₅CH₃ + AlCl₃ + HCl

Addition of electrolytes:
A negative ion causes the precipitation of positively charged sol and vice versa. When the valency of ion is high, the precipitation power is increased.
For example, the precipitation power of some cations and anions varies in the following order
\(\mathrm{Al}^{3+}>\mathrm{Ba}^{2+}>\mathrm{Na}^{+} \text {, Similarly }\left[\mathrm{Fe}\left(\mathrm{CN}_{6}\right)\right]^{3-}>\mathrm{SO}_{4}{ }^{2-}>\mathrm{Cl}^{-}\)
The precipitation power of electrolyte is determined by finding the minimum concentration (millimoles/lit) required to cause precipitation of a sol in 2 hours. This value is called flocculation value. The smaller the flocculation value greater will be precipitation.

b) Both (A) and (R) are true but (R) does not explain (A)

b) Both (A) and (R) are true but (R) does not explain (A)

d) Heat of adsorption is large

(i) An electrical arc is struck between electrodes dispersed in water surrounded by ice.
(ii) When a current of 1 amp 1100v is passed an arc produced forms vapours of metal which immediately condense to form colloidal solution.
(iii) By this method, colloidal solution of many metals like copper, silver, gold, platinum, etc. can be prepared alkali hydroxide is added as an stabilising agent for the colloidal solution.

Food:
Food stuffs like milk cream, butter, etc are present in colloidal form.
Medicines:
Antibodies such as penicillin and streptomycin are produced in colloidal form for suitable injections. Colloidal gold and colloidal calcium are used as tonics. Milk of magnesia is used for stomach troubles. Silver sol protected by gelatine known as Argyrol is used as eye lotion.
In Industry:
Colloids find many applications in industries
(i) Water purification:
Purification of drinking water is activated by coagulation of suspended impurities in water using alums containing Al³⁺.
(ii) In washing:
The cleansing action of soap is due to the formation of emulsion of soap molecules with dirt and grease.
(iii) Tanning of leather:
Skin and hides are protein containing positively charged particles which are coagulated by adding tannin to give hardened leather for further application. Chromium salts are used for the purpose. Chrome tanning can produce soft and polishable leather.
(iv) Rubber industry:
Latex is the emulsion of natural rubber with negative particles. By heating rubber with sulphur, vulcanized rubbers are produced for tyres, tubes, etc.
(v) Sewage disposal:
Sewage contains dirt, mud and wastes dispersed in water. The passage of electric current deposits the wastes materials which can be used as a manure.
(vi) Cortrell's precipitator:
Carbon dust in air is solidified by Cottrell's precipitator. In it, a high potential difference of about 50,000V is used. The charge on carbon is neutralized and solidified. Thus the air is free from carbon particles.
(vii) The blue colour of the sky in nature is due to Tyndall effect of air particles.
(viii) Formation of delta:
The electrolyte in sea and river water coagulates the solid particles in river water at their intersection. So, the earth becomes a fertile land.
(ix) Analytical application:
Qualitative and quantitative analysis are based on the various properties of colloids.

(i) Effective and efficient conversion is the special characteristic of enzyme catalysed reactions. An enzyme may transform a million molecules of reactant in a minute 
For Eg: \({ 2H }_{ 2 }{ O }_{ 2 }\longrightarrow { 2H }_{ 2 }O+{ O }_{ 2 }\)
For this reaction, the activation energy is 18k cal/mole without a catalyst  With colloidal platinum as a, catalyst the activation energy is 11.7kcal /mole. But with the enzyme catalyst the activation energy of this reaction is less than 2kcal/ mole.
(ii) Enzyme catalysis is highly specific in nature.
(iii) Enzyme catalysed reaction has maximum rate at optimum temperature
(iv) The rate of enzyme catalysed reactions varies with the pH of the system. The rate is maximum at a pH called optimum pH.
(v) Enzymes can be inhibited i.e. poisoned activity of an enzyme is decreased and destroyed by a poison. The physiological action of drugs is related to their inhibiting action.
(vi) Catalytic activity of enzymes is increased by coenzymes or activators.