The negatively charged sol among the following is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Sb2S3 sol
The charge on a sol depends on the ions it adsorbs: a metal sulphide sol such as \( \ce{Sb2S3} \) adsorbs \( \ce{S^2-} \)/\( \ce{HS-} \) ions and is negatively charged.
Why the other options are incorrect
Option (1) Fe(OH)3 sol — Incorrect. A hydrated metal oxide; it adsorbs \( \ce{Fe^{3+}} \) and is positively charged.
Option (2) Haemoglobin — Incorrect. Listed among the positively charged sols (blood).
Option (3) TiO2 sol — Incorrect. A metal oxide sol; positively charged.
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):
Charge on Colloidal Particles – …
