Question

The separation of colloidal particles (or purification of sol) from particles of molecular dimensions is known as :

• A. photolysis
• B. dialysis
• C. pyrolysis
• D. peptization

Answer 1

Answer: (B)

dialysis

Photodissociation, photolysis, or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule. Photodissociation is not limited to visible light.

Dialysis, separation of suspended colloidal particles from dissolved ions or molecules of small dimensions by means of their unequal rates of diffusion occurs through the pores of semipermeable membranes. This process was first employed in 1861 by a British chemist, Thomas Graham. If such a mixture is placed in a sack made of parchment and suspended in water, the ions and small molecules pass through the membrane, leaving the colloidal particles in the sack.

Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen (or any halogen). It involves the simultaneous change of chemical composition and physical phase, and is irreversible.

Peptization is the process responsible for the formation of stable dispersion of colloidal particles in dispersion medium. In other words it may be defined as a process of converting a precipitate into colloidal sol by shaking it with dispersion medium in the presence of small amount of electrolyte.