Question

Tyndall effect is exhibited by:

• A. True solutions
• B. Suspensions
• C. Colloidal solutions
• D. Crystals

Hint:

The Tyndall effect is a characteristic of colloidal solutions due to the scattering of light by larger particles.

Answer 1

The Correct Option is C

The Tyndall effect is a phenomenon observed when a beam of light is scattered by particles in a medium. It is typically exhibited by colloidal solutions. Let's examine why this is the case in comparison with other systems mentioned:

1. True Solutions: True solutions have solute particles, which are molecularly dispersed and far too small (less than 1 nm) to scatter light. Therefore, true solutions do not exhibit the Tyndall effect.

2. Suspensions: While suspensions have larger particles that can scatter light, these particles are heavy enough to eventually settle out due to gravity, thus suspensions are not stable and inconsistent in exhibiting the Tyndall effect.

3. Colloidal Solutions: Colloids contain particles of intermediate size (1-1000 nm) that are large enough to scatter light, but small enough to remain suspended in the medium without settling. This stability and particle size make colloidal solutions ideal for displaying the Tyndall effect, where the path of a light beam can be visibly observed due to scattered light.

4. Crystals: Crystals have a solid, ordered structure and do not allow for the scattering of light in the manner a liquid or gas medium does, hence they do not exhibit the Tyndall effect.

In conclusion, the correct answer is: Colloidal solutions.

Answer 2

Whether a mixture shows the Tyndall effect depends on whether its dispersed particles fall in a size range that scatters visible light, roughly 1 to 1000 nanometres, without being so heavy that they settle out. Let's check each type of mixture against that range.

1. True solutions: The particles here are single ions or molecules, under 1 nanometre, far too small to scatter light, so no Tyndall effect appears.
2. Suspensions: These have particles bigger than about 1000 nanometres, visible or nearly visible to the eye, which do scatter light but also settle out under gravity fairly quickly, making the mixture unstable and not the standard example used for this effect.
3. Colloidal solutions: Colloid particles sit in the 1 to 1000 nanometre range, big enough to scatter light strongly and stay suspended without settling, which is exactly the combination that produces a clear, lasting Tyndall effect.
4. Crystals: A crystal is an ordered solid structure, not particles dispersed through a liquid or gas medium, so the concept of light scattering through a dispersed medium does not even apply here.

Only colloids combine light-scattering particle size with long-term stability in the medium, which is why they are the standard example of the Tyndall effect.

So the correct answer is colloidal solutions.