Answer the following:

(a) Why is ester hydrolysis slow in the beginning and then becomes faster after some time?

(b) In a solution of methylene blue, animal charcoal is added, the solution is then well shaken. What will be observed and why?

(c) Give an example of oil in water emulsion.

OR

Define the following:

(a) Associated colloids (b) Electrophoresis (c) Zeta potential

(a) Ester on hydrolysis forms alcohol and acid. The acid produced acts as a catalyst and the rate of reaction increases. Thus, the reaction becomes fast due to formation of more and more acid with time.

(b) When animal charcoal is added in a solution of methylene blue, it is observed that the solution turns colourless. It is because the molecules of the methylene blue are adsorbed on the surface of charcoal and the solution becomes colourless.

(c) An example of oil in water emulsion is milk.

OR

(a) Associated colloids are substances which behave as normal electrolytes at low concentration but at higher concentration form aggregates and exhibit colloidal behavior.

(b) Electrophoresis is the process of migration of charged colloidal particles towards oppositely charged electrodes under the influence of an electric field.

(c) Zeta potential is the potential difference developed between the two oppositely charged layers i.e. the fixed and diffused layer around colloids.