Conversion of freshly prepared precipitate into the colloidal solution is known as
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Peptization
In peptization a small amount of an electrolyte (the peptizing agent) is added: the precipitate particles adsorb one kind of its ions, become charged, repel one another and break up into colloidal particles. For example, freshly precipitated \( \ce{Fe(OH)3} \) shaken with a little \( \ce{FeCl3} \) solution gives a reddish-brown, positively charged sol of \( \ce{Fe(OH)3} \). The reverse change, sol to precipitate, is coagulation.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Peptization – “Peptization may be defined as the process of converting a precipitate into colloidal sol by shaking it with dispersion medium in the presence of a small amount of electrolyte. The electrolyte used for this purpose is called peptizing agent.”