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Q90
(NDA-II/2023)
Science & Technology › Basic Science (Physics, Chemistry, Biology)
Official Key
What is the action of litmus on ethanol ?
Explanation
Ethanol (C2H5OH) is a neutral organic compound. While it contains a hydroxyl (-OH) group, it does not readily ionize in aqueous solutions to release hydrogen ions (H+) or hydroxide ions (OH-) in concentrations sufficient to affect pH indicators.
- Acids: Turn blue litmus paper red by releasing H+ ions.
- Bases: Turn red litmus paper blue by releasing OH- ions.
Ethanol has a pKa value of approximately 15.9, which is very close to that of water (14–15.7), making it effectively neutral under standard conditions. Therefore, it does not change the color of either red or blue litmus paper. This lack of reaction confirms that litmus is neutral towards ethanol, supporting Option A.
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