Question

How would you distinguish experimentally between an alcohol and a carboxylic acid?
(i) Sodium bicarbonate test
(ii) Reaction with alkali metal
(iii) Iodoform test
(iv) None of these

Answer 1

Hint: Solve this question by considering the reactivity of the compounds. Carboxylic acid, being an acid, has a high tendency to donate a proton and is very reactive. Whereas, alcohols are mildly acidic. They possess the tendency to donate protons, but they are not as reactive.

Complete step by step answer:
Sodium bicarbonate test is the best method to experimentally distinguish carboxylic acid from alcohol because even phenol does not respond to this test.
In this test, carboxylic acid reacts with sodium bicarbonate to form sodium acetate and a brisk effervescence of carbon dioxide. This effervescence is what indicates the carboxylic acid.
\[RCOOH+NaHC{{O}_{3}}\to RCOONa+{{H}_{2}}O+C{{O}_{2}}\uparrow \]
Therefore, the answer is – option (a) – an alcohol and a carboxylic acid can be experimentally distinguished by Sodium bicarbonate test.

Additional Information:
Sodium bicarbonate test is also known as sodium hydrogen-carbonate test.

Note: Other than sodium bicarbonate test, carboxylic acids can also be detected by –
1- Litmus Test
Carboxylic acid (like any other acid) turns blue litmus red. Alcohols do not respond to this test except phenol.
2- Ester Test
Carboxylic acids on esterification give off a sweet smell.
3- Fluorescein Test
This test is given by dicarboxylic acid, which gives acid anhydride on heating.