(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.

 (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.

209. State Hardy-Schulze rule.

(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.