Question

Which of the following show tyndall effect?
A. Aqueous solution of soap below critical micelle concentration
B. Aqueous solution of soap above critical micelle concentration
C. Aqueous solution of sodium chloride
D. Aqueous solution of sugar

Answer 1

Hint: When light is passed through colloid solution it scatters it doesn’t follow a straight path. This is known as Tyndall effect. For any solution to show Tyndall effect it must be a colloid solution.

Complete step-by-step answer:
In Tyndall effect when a light beam is passed through a solution it doesn’t follow a straight path it gets scattered due to the particles present in the colloid solution obstructing their path.
Colloid solutions also known as colloid suspensions are the mixtures in which the solute remains suspended in the solution. Example milk in water.
So, for any solution to show tyndall effect they should be colloidal solutions.
For formation of micelles two conditions are there:
- Micelle formation only takes above kraft temperature.
- Micelle formation only takes above a particular concentration known as critical micelle concentration.

Therefore, below a critical micelle formation soap solution doesn’t act as colloid.
An aqueous solution of sodium chloride and sugar are true solutions i.e. sodium chloride and sugar completely dissolves in water forming a transparent solution with no suspended particles.
Aqueous solution below critical micelle concentration is not a colloid solution whereas aqueous solution of soap above critical micelle concentration is a colloidal solution.
Therefore, tyndall effect will be shown by soap solution above critical micelle concentration. The correct answer is B.

Note: Tyndall effect totally depends on whether the solution is colloidal or not. Soap solution is colloidal or not depending on kraft temperature and critical micelle concentration. Sugar and sodium chloride solutions are true solutions as they are completely soluble in water.