Answer:
Purification of colloidal solutions:
Dialysis: It is the process of separating colloidal particles from those of crystalloids by diffusing the mixture through a parchment or animal membrane. Colloidal particles do not pass through while those of crystalloids do. The impure sol is filled into a cellophane bag, which is suspended in a vessel containing distilled water. The crystalloid particles pass through while colloidal particles do not.
Ultra filtration: It is the process of purifying a colloidal particle by treatment with a filter paper treated with colloidion which reduces the pore size of the filter paper. The sol is poured over the ultrafilter which permits the electrolytic solution to pass but retains the colloidal particles.
Answer:
Explain the following observations:
(a) Ferric hydroxide sol gets coagulated on addition of sodium chloride solution.
(b) Cottrell’s smoke precipitator is fitted at the mouth of the chimney used in factories.
(c) Physical adsorption is multi layered, while chemisorption non layered.
Answer:
(a) When sodium chloride is added to ferric hydroxide sol, the sol gets coagulated. This is because the Cl– ions from NaCl neutralize the +ve charge on Fe(OH)3 sol.
Fe2O3.xH2O/Fe3+
(b) Smoke coming out of the chimenys contain a lot of unburnt carbon particles smoke is the colloidal solution of the solid particles such as carbon arsenic dust particles etc.
These particles are injurious to health and have to be precipitated since carbon particlesare charged particles and cannot be precipitated, thus metal plate of oppositely charged particles is used for their precipitation.
This is done by the cottrell smoke precipitator which neutralizes the charge on the carbon.
(c) Physical adsorption is multilayered because forces between adsorbate and adsorbent molecule are of Van der Waal’s type.
Chemisorption is non-layers because forces of attraction are of chemical bond type.
increases with increase in pressure, it is physical adsorption. If it first increases and then becomes independent of pressure then it is chemical adsorption.
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