Question

Which one of the following will exhibit Tyndall effect ?

• A. Potassium permanganate + Water
• B. Chalk powder + Water
• C. Potash alum + Water
• D. Sugar + Water

Answer 1

The correct option is B

Chalk powder + Water

The explanation for the correct option

Option B- Chalk powder + Water

Chalk powder + Water will exhibit the Tyndall effect.

Tyndall effect

1. Particles can easily scatter a beam of visible light passing through them. This scattering of a beam of light is called the Tyndall effect.
2. It is shown by colloids and Suspension.
3. Chalk powder + Water is a suspension.
4. Suspension - Suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium.
5. Its size is greater than $1\mathrm{nm}$.

The explanation for the incorrect option

Potassium permanganate$\left({\mathrm{KMnO}}_4\right)$ + Water, Potash alum$\left(\mathrm{KAl}{\left({\mathrm{SO}}_4\right)}_2·12{\mathrm{H}}_2\mathrm{O}\right)$ + Water, Sugar $\left({\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\right)$+ Water makes a true solution.

1. True solution: It is a homogeneous mixture that contains small solute particles that are dissolved throughout the solvent.
2. The particle size of a true solution is smaller than $1\mathrm{nm}$ i.e., ${10}^{-9}$ the meter in diameter. Therefore, they cannot be seen by the naked eye or even with a microscope.

Hence option (B) is correct.