Antiseptics and disinfectants either kill or prevent growth of micro-organism. Identify which of the following statements is not true?
(A) Disinfectants harm the living tissues.
(B) A 0.2% solution of phenol is an antiseptic while 1% solution acts as a disinfectant.
(C) Chlorine and Iodine are used as strong disinfectants.
(D) Dilute solution of boric acid and hydrogen peroxide are antiseptics
(E) Iodoform is also used as an antiseptic for wounds.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (C) only
(A) Disinfectants harm the living tissues — True. That is why disinfectants are applied to inanimate objects (floors, drains, instruments) and not to wounds.
(B) 0.2% phenol is an antiseptic, 1% phenol a disinfectant — True. The same substance acts as antiseptic or disinfectant depending on its concentration.
(C) Chlorine and iodine are used as strong disinfectants — False. Chlorine is a disinfectant in very low concentration (0.2 to 0.4 ppm in water), but iodine is a powerful antiseptic: its 2-3% solution in alcohol-water (tincture of iodine) is applied on wounds.
(D) Dilute boric acid and hydrogen peroxide are antiseptics — True. Dilute boric acid is a weak antiseptic for the eyes; dilute \( \ce{H2O2} \) is used to clean wounds.
(E) Iodoform is used as an antiseptic for wounds — True.
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 – “… Iodine is a powerful antiseptic. Its 2-3 per cent solution in alcohol-water mixture is known as tincture of iodine. It is applied on wounds. Iodoform is also used as an antiseptic for wounds. Boric acid in dilute aqueous solution is weak antiseptic for eyes.”
Antiseptics and Disinfectants – “… 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.”