Long Answer Type(a) Which will absorb more gas, a lump of charcoal or its powder and why?
(b) Describe the preparation of the following colloidal solutions. Name the method used in each case (i) silver sol, (ii) sulphur sol.
Answer:
The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption. The molecular species or substance, which concentrates or accumulates at the surface is termed adsorbate and the material on the surface of which the adsorption takes place is called adsorbent.
There are mainly two types of adsorption of gases on solids:
i)physisorption
ii)chemisorption
The extent of adsorption increases with the increase of surface area of the adsorbent. Thus, finelydivided lamp of charcoal powder and porous substances having large surface areas are good adsorbents.
b)
Silver sol can be prepared by the double decomposition reaction.
In this dilute solution of silver nitrate react with potassium chloride to give silver chloride solution.
AgNO3 + KCl -----> AgCl + KNO3
sulphur sol may be prepared by oxidation of hydrogen sulphide by bromine.
H2S +Br2---> S + 2HBr
Explain What is observed when:
(a) A beam of light is passed through a colloidal solution of As2S3
(b) An electrolyte (NaCl) is added to ferric hydroxide sol.
(c) An electric current is passed through a colloidal solution.
Short Answer TypeLong Answer TypeIllustrate with example:
(i) Lyophilic and Lyophobic sols.
(ii) Multimolecular and macromolecular colloids.
(iii) Homogeneous and Heterogeneous catalysis.
Short Answer TypeLong Answer Type
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