Which aldehyde is used to preserve biological specimens?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Formaldehyde
Biological specimens are kept in formalin, a 40% aqueous solution of formaldehyde (methanal, HCHO). Formaldehyde reacts with the proteins of the tissue and cross-links them, so the tissue hardens and keeps its shape, and it kills the bacteria and fungi that would make the specimen decay.
NCERT (2026-27 edition):
Uses of Aldehydes and Ketones – …
