Question

The size of colloidal particles ranges between:
(A) \[{\text{1}}{{\text{0}}^{ - 7}}{\text{ - 1}}{{\text{0}}^{ - 9}}{\text{ cm}}\]
(B) \[{\text{1}}{{\text{0}}^{ - 9}}{\text{ - 1}}{{\text{0}}^{ - 11}}{\text{ cm}}\]
 (C) \[{\text{1}}{{\text{0}}^{ - 5}}{\text{ - 1}}{{\text{0}}^{ - 7}}{\text{ cm}}\]
 (D) \[{\text{1}}{{\text{0}}^{ - 2}}{\text{ - 1}}{{\text{0}}^{ - 3}}{\text{ cm}}\]

Answer 1

Hint: Particles of colloids cannot be seen with naked eye but if high resolution and high-power optical devices such as electron microscopes are used, these particles can be seen.

Complete step by step answer: A colloid is a mixture in which one of the substances is split into very minute particles which are dispersed throughout a second substance. The substance which is dispersed is called a dispersed phase whereas the one in which the first substance is distributed is called a dispersion medium. Size of colloid particles generally ranges between, 1 to 1000 nanometres i.e. \[{\text{1}}{{\text{0}}^{ - 5}}{\text{ - 1}}{{\text{0}}^{ - 7}}{\text{ cm}}\].

Hence, option C is correct.

Additional information: Sometimes, when light falls on colloids, particles of colloids show scattering of this light. This phenomenon is called the Tyndall effect. Colloids that show tyndall effect are generally translucent in nature.
Mobility of the phases and charges on the particles affect the interactions between colloid particles. The particles generally carry electrical charges and hence show electrostatic interactions i.e. they might attract or repel each other. The particles might also have permanent or induced dipoles and hence there also exist Van der Waals forces between them. Even if some particles might not have a permanent dipole, fluctuations of the electron density may give rise to a temporary dipole in a particle.

Note: Size of constituent particles is a fundamental difference between solutions and colloids. The commercial application of colloids is that it is used as a coagulating and thickening agent. The dispersed phase does not settle at the bottom and remains suspended within the mixture.