Define the following with a suitable example, of each:

a. Coagulation

b. Multimolecular colloid

c. Gel

OR

a. Out of starch and ferric hydroxide sol, which one can easily be coagulated and why?

b. What is observed when an emulsion is centrifuged?

c. What is the role of promoters and poisons in catalysis?

a. Coagulation: The precipitation of particles of the dispersed phase in a sol is known as coagulation. Example: Formation of Delta.

b. Multimolecular colloid: When large number of atoms or molecules aggregate to form species having size in the colloidal range (having diameter less than 10^-9m or 1 nm), such colloids are known as multimolecular colloids. Example- Gold sols.

c. Gel: When liquid is dispersed in solid then it is called as gel. Example: Butter, cheese

OR

a. Ferric hydroxide sol can be easily coagulated than starch sol because it is lyophobic sol and hence can easily be precipitated.

b. When an emulsion is subjected to centrifugal force, the revolutions of the liquid occur at very high speeds. This leads to demulsifying or separation of the two liquids. The liquid which is less dense or the lighter liquid will stand on the top and the heavier or the denser liquid will stay down.

c. Promoters are the substances which increase the efficiency of catalyst whereas poison are the substances that decreases the efficiency of catalyst.