Short Answer Type(a) How can a colloidal solution and true solution of the same colour be distinguished from each other ?
(b) List four applications of adsorption.
Explain the following observations:
(a) Lyophilic colloids are more stable than lyophobic colloid.
(b) Coagulation takes place when sodium chloride solution is added to a colloidal solution of ferric hydroxide.
(c) Sky appears blue in colour.
Answer:
a) Particles of dispersed phase have great affinity for the dispersion medium. They are self stabilised because of strong attractive forces operating between the suspended particles and the dispersion medium. e.g. gums gelatin.
b) When freshly precipitate Fe(OH)3 is shaken with little amount of dilute solution of FeCl3 (electrolyte)
Peptization process takes place by converting the Fe(OH)3 precipitate into colloidal solution positively charged solution of Fe(OH)3.
c) Transmitted light is made up of a spectrum of colors the longest wavelength of light are on red end of spectrum and the shortest wavelength areon the blue/ violet end of the spectrum.
When transmitted light such as sunlight enters ours atmosphere it colloide with dust and water droplet and scattered violet/blue light.
But because our eyes are more sensitive to blue color thus we see blue color of sky.
(a) In which of the following does adsorption take place and why?
(i) Silica gel placed in the atmosphere saturated with water.
(ii) Anhydrous CaCl2 placed in the atmosphere saturated with water.
(b) How does BF3 act as a catalyst in industrial process?
(c) Give an example of shape selective catalysis.
Long Answer Type(a) Of NH3 and CO2 which will be adsorbed more readily on the surface of charcoal and why?
(b) How are multimolecular colloids different from macro-molecular colloids?
(c) State the principle of electro-dialysis.
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