Surface Chemistry (Chapter 5) => 3 Marks Questions Answers

These are 3 Marks Questions Answers on "Surface Chemistry" (Chapter 5). Practice for CBSE EXAMINATION, CBSE NEET etc.

Questions carrying 3 marks:

1.     What is the difference between multimolecular and macromolecular colloids? Give one example of each.

2.     Explain the terms coagulation, dialysis and Tyndall effect.

3.     Explain the following terms alcosol, aerosol and hydrosol.

4.     Give specific term to show the effect of the following process.

a)  Ferric hydroxide is mixed with arsenic sulphide sol

b)  Ferric chloride solution is mixed with freshly prepared precipitate of ferric hydroxide.

c)  H₂S is passed through arsenic oxide solution.

5.      What is emulsion and what are the types with example each?

Answer key

1.      Multimolecular colloids are formed by the aggregation of large number of molecules (for e.g. S₈) . Macromolecular colloids are due to large size of molecule themselves (e.g. starch) so large that their size lies in the colloidal range.

2.      Coagulation is the process of aggregation of colloidal particles so as to change them into large sized particles which ultimately settles as precipitate.

Dialysis is the process of separating the particles of colloids from those of crystalloids by diffusion of the mixture through parchment membrane.

Scattering of light through colloidal solution by the colloid particles is called Tyndall effect.

3. Alcosol is colloidal dispersion having alcohol as dispersion medium e.g. collodion .Aerosol is colloidal dispersion of a liquid in gas for e.g. fog. Hydrosol is colloidal dispersion of a solid in liquid e.g. starch sol or egg albumin sol.

4.    a) Coagulation b) Peptisation  c) Double decomposition.

5.       Emulsion; It is a colloid dispersion in which both the dispersed phase and dispersion medium are liquids. their types are O/W i.e. oil in water emulsion W/O water in oil emulsion

a)      O/W in which oil is the dispersed phase and water as dispersion medium for e.g. milk vanishing cream

b)      W/O in which water is the dispersed phase and oil as dispersion medium for e.g. butter and cold cream.