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Chapter 13: Problem 88

Explain how each of the following factors helps determine the stability or instability of a colloidal dispersion: (a) particulate mass, (b) hydrophobic character, (c) charges on colloidal particles.

Short Answer

Expert verified
The stability of colloidal dispersions is determined by (a) particulate mass, in which smaller particles with lower mass have better stability; (b) hydrophobic character, where particles with a low hydrophobic character are well-dispersed and stable in water; (c) charges on colloidal particles, as similar charges repel each other, preventing aggregation and maintaining stability, while opposite or no charges promote aggregation and instability.

Step by step solution

01

(a) Particulate Mass

Particulate mass refers to the size and weight of the colloidal particles. Greater mass, or larger particles, can cause the particles to settle more quickly due to gravitational forces, leading to instability in the colloidal dispersion. Smaller particles with lower mass are less affected by gravity and can remain suspended for longer periods, contributing to better stability.
02

(b) Hydrophobic Character

The hydrophobic character of the colloidal particles refers to their tendency to repel water. If the particles have a high hydrophobic character, they will tend to be poorly dispersed in an aqueous medium, leading to agglomeration and hence, instability. Conversely, particles with low hydrophobic character tend to be better dispersed in water, promoting stability of the colloidal dispersion.
03

(c) Charges on Colloidal Particles

The charges present on the surface of colloidal particles can greatly influence the stability of the dispersion. Generally, particles with similar charges repel each other, preventing them from aggregating and maintaining the stability of the dispersion. Whereas, if the particles have no charge or opposite charges, they are likely to come together and form larger aggregates, causing instability in the colloidal dispersion. The presence of charged particles or adsorbed ions can therefore create a stabilizing effect on colloidal dispersions.

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