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NEET levelSingle correct optionDifficulty 1 of 3g2111

Which reagent can be used to distinguish a carboxylic acid such as $C X_{6} H X_{5} COOH$ from a simple phenol such as $C X_{6} H X_{5} OH$ by a simple test tube reaction?

AAqueous $NaHCO X_{3}$ (effervescence of $CO X_{2}$ with the carboxylic acid only)
BAqueous $NaOH$ (both dissolve)
CMetallic sodium (both give $H X_{2}$ )
DAqueous $NaCl$

Answer: A

Carboxylic acids (

p K_{a} \approx 4

-5) are stronger than carbonic acid (

p K_{a}

6.4), so they liberate

CO X_{2}

from

NaHCO X_{3}

. Phenol (

p K_{a}

10.0) is weaker than carbonic acid and does not.

NaOH

and Na react with both, and

NaCl

with neither. So

NaHCO X_{3}

distinguishes them.

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