Statement I : Micelles are formed by surfactant molecules above the critical micellar concentration (CMC).

Question

Read the following questions and answer as per the direction given below : 

(a) Statement I is true; Statement II is true; Statement II is a correct explanation of Statement I. 

(b) Statement I is true; Statement II is true; Statement II is not the correct explanation of Statement I. 

(c) Statement I is true; Statement II is false. 

(d) Statement I is false; Statement II is true.

Statement I : Micelles are formed by surfactant molecules above the critical micellar concentration (CMC). 

Statement II : The conductivity of a solution having surfactant molecules decreases sharply at the CMC.

Answer 1

The correct option (b) Statement I is true; Statement II is true; Statement II is not the correct explanation of Statement I. 

Explanation:

At a certain concentration surfactant molecules start to aggregate and form micelle, the concentration is called critical micellisation concentration (CMC).

Aggregation of surfactant molecules (ions; RCOO^-) ie. micelle formation cause effective fall in number of free ions to conduct electricity, thus conductivity decreases at CMC.