Question

When propionic acid is treated with aqueous sodium bicarbonate aqueous $C{O_2}$ is liberated. The C from $C{O_2}$ comes from
(A) Methyl group
(B) Carboxylic acid group
(C) Methylene group
(D) Bicarbonate

Answer 1

Hint: We know that when acid and a base are reacted, respective salt and water are formed. When carboxylic acid reacts with aqueous sodium bicarbonate it releases carbon dioxide along with the formation of respective salt and water. It is an acid-base reaction.

Complete step by step answer:
We know that carboxylic acids reacting with aqueous sodium bicarbonate form sodium salt of carboxylic acid, carbonic acid which is unstable which further forms carbon dioxide and a water molecule.
Now coming to the given question we will carry out the given reaction. We will carry out the reaction between propionic acid and aqueous sodium bicarbonate. The reaction will be as follows

${C_2}{H_5}COOH + NaHC{O_3} \to {C_2}{H_5}COONa + {H_2}O + C{O_2} \uparrow $

Here the formation of water takes place by taking one hydrogen from propionic acid, one from sodium bicarbonate, and one oxygen from sodium bicarbonate. The remaining carbon dioxide is formed from bicarbonate. So the C of $C{O_2}$ comes from bicarbonate.
Therefore the C of $C{O_2}$ comes from bicarbonate.

So, the correct answer is Option D .

Additional information:
When carboxylic acids react with sodium bicarbonate solution carbon dioxide is evolved with a brisk effervescence along with sodium salt of the acid. This reaction is used as a test to differentiate carboxylic acid from phenol.Also, phenols are less acidic than carboxylic acid and they don’t react with a carboxylic acid to form salts.

Note: Carboxylic acids form salts with sodium bicarbonate irrespective of their solubility in that very compound. In these types of reactions the carboxylic acids act like inorganic acids that are, they neutralize basic compounds.