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What is peptization and what is a precipitate? How does peptization help to form a colloidal sol?

What is peptization and what is a precipitate? How does peptization help to form a colloidal sol?
 

Grade:12

3 Answers

Aarti Gupta
askIITians Faculty 300 Points
9 years ago
Peptization – The process of peptization involves the conversion of a precipitate into colloidal sol by shaking it with dispersion medium in the presence of small amount of electrolyte.The electrolyte used for this purpose is called the peptizing agent.For ex-Reddish brown colored colloidal solution is obtained on adding small quantity of ferric chloride solution to the freshly precipitated ferric hydroxide.

Precipitate – Its an insoluble solid that emerges freom a liquid solution.

Process of peptization is generally used to convert a freshly prepared precipitate into a colloidal sol.During this process,the precipitate adsorbs one of the ions of the electrolyte on its surface,which causes the development of positive or negative charge on precipitates,which ultimately break up into smaller particles of the size of a colloid.In this way the process of peptization help to form a colloid sol.
DEEPAK C. SATHEESAN
37 Points
9 years ago
Thank you madam, but I did not understand how the precipitate aborbs the ions and why it causes breaking up of the particles into a size in the colloidal range.
 
Aarti Gupta
askIITians Faculty 300 Points
8 years ago
As small amount of electrolyte is added,there is preferential adsorption of positive or negative ions from the electrolyte by the precipitate.This is the peptizing action of ppt. and this is due to the adsorption of either charge.Particles carrying similar charges get separated,giving smaller charged colloidal particles.As in the above example on adding FeCl3,Fe3+ ions are adsorbed by Fe(OH)3 resulting in positive charge on the surface.Similar charged particles gets separated due to electrostatic repulsion and smaller charged colloidal particles of the type Fe(OH)3Fe3+ are formed.

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