Antiseptics and disinfectants either kill or prevent growth of microorganisms. Identify which of the following statement/s is not true.
(A) Disinfectants are applied to living tissues.
(B) Dilute solution of boric acid and hydrogen peroxide are strong antiseptics
(C) A \(0.2\%\) solution of phenol is an antiseptic while \(1\%\) solution acts as disinfectants.
(D) Chlorine and sulphur dioxide in very low concentrations are disinfectants.
Choose the correct answers from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A and B only
Antiseptics are applied to living tissues such as wounds, cuts and skin; disinfectants are applied to inanimate objects such as floors, drainage systems and instruments. The same substance can act as either, depending on its concentration.
(A) Disinfectants are applied to living tissues. — False. Disinfectants are applied to non-living objects; it is antiseptics that are applied to living tissues.
(B) Dilute solution of boric acid and hydrogen peroxide are strong antiseptics — False. Dilute boric acid and hydrogen peroxide are weak antiseptics.
(C) A 0.2% solution of phenol is an antiseptic while 1% solution acts as disinfectants. — True. Phenol is an antiseptic at 0.2% and a disinfectant at 1%.
(D) Chlorine and sulphur dioxide in very low concentrations are disinfectants. — True. Chlorine at 0.2 to 0.4 ppm in water and sulphur dioxide in very low concentrations are disinfectants.
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):
Antiseptics and Disinfectants – “… Antiseptics are applied to the living tissues such as wounds, cuts, ulcers and diseased skin surfaces.”
Antiseptics and Disinfectants – “… Boric acid in dilute aqueous solution is weak antiseptic for eyes. Disinfectants are applied to inanimate objects such as floors, drainage system, instruments, etc. Same substances can act as an antiseptic as well as disinfectant by varying the concentration. For example, 0.2 per cent solution of phenol is an antiseptic while its one percent solution is disinfectant. Chlorine in the concentration of 0.2 to 0.4 ppm in aqueous solution and sulphur dioxide in very low concentrations, are disinfectants.”