Question

The particle size in a colloidal solution is:

• A. 1 Å – 10 Å
• B. 10 Å – 2000 Å
• C. More than 2000 Å
• D. Less than 1 Å

Hint:

Colloidal solutions have particle sizes in the range of 10 Å to 2000 Å, which is why they exhibit the Tyndall effect.

Answer 1

The Correct Option is B

To determine the characteristic particle size range for colloidal solutions, we need to understand the nature of colloids in chemistry. A colloidal solution, which is a type of heterogeneous mixture, consists of particles that are dispersed throughout the solution but do not settle out due to gravity like those in suspensions.

The key factor distinguishing colloids from other types of mixtures, such as solutions and suspensions, is the size of its dispersed particles:

• True solutions: Particle size < 1 Å
• Colloidal solutions: Particle size between 10 Å and 2000 Å
• Suspensions: Particle size > 2000 Å

This information helps us identify the correct option for the particle size range of colloidal solutions from the given options:

• 1 Å – 10 Å (True solution)
• 10 Å – 2000 Å (Correct for colloids)
• More than 2000 Å (Suspension)
• Less than 1 Å (True solution)

Therefore, the particle size in a colloidal solution is 10 Å – 2000 Å.

Answer 2

The question asks which particle-size range describes a colloidal solution. Check each range against how particles of that size actually behave in a liquid.

1. 1 Å - 10 Å: particles this small pass straight through filter paper and even through a fine membrane, and they never scatter a beam of light. That is the behavior of a true solution, not a colloid, so this range is too small.
2. 10 Å - 2000 Å: particles in this range are too small to settle under gravity but large enough to scatter light, producing the Tyndall effect. They also get held back by a fine membrane while still passing ordinary filter paper. This matches how a colloidal solution behaves.
3. More than 2000 Å: particles this large settle out on standing and get caught by ordinary filter paper. This is how a suspension behaves, not a colloid.
4. Less than 1 Å: there is no real particle, ion, or small molecule at this size; even solute particles in a true solution are larger than this.

Only the 10 Å - 2000 Å range shows the light-scattering, non-settling behavior of a colloid.

So the correct answer is 10 Å - 2000 Å.