Question

The anhydride of carbonic acid is:
(A) $CO$
(B) $C{O_2}$
(C) ${C_3}{O_2}$
(D) None of these

Answer 1

Anhydrides means without water. They are the organic compounds that are obtained after the removal of water from other organic compounds. The organic anhydrides are used to introduce the acyl group in organic synthesis.

Complete answer: Carbonic acid is an organic compound made up of carbon, oxygen, and hydrogen. It is a dibasic acid. The chemical formula of carbonic acid is ${H_2}C{O_3}$. It is a weak acid and forms salts of carbonates and bicarbonates. In the structure of carbonic acid, one carbon-oxygen double bond is present, and two single carbon-oxygen bonds. The oxygen atoms are further bonded with one hydrogen atom each. Since ${H_2}C{O_3}$ is a weak acid, it is highly unstable and gets dissociated into hydrogen ion (${H^ + }$) and bicarbonate ions ($HCO_3^ -$). It is the product of dissolution and hydrolysis of carbon dioxide in water.
$C{O_2} + {H_2}O\, \rightleftharpoons {H_2}C{O_3}$
As we know that upon decomposition of Carbonic acid, we get $C{O_2}$ and ${H_2}O$. Here, carbon dioxide is regarded as the anhydride of carbonic acid.

ADDITIONAL INFORMATION: Carbonic acid is also obtained as a by-product in the process of industrial fermentation or through the burning of fossil fuels at an industrial level. The bicarbonate ion is also responsible for the transportation of carbon dioxide in the human body by the process of gas exchange. The carbonic anhydrase enzymes help in the conversion of carbon dioxide and water into the dissociated ions of carbonic acid. This results in the production of bicarbonate anions which are soluble in the blood plasma.

Hence, Option (B) is correct.

Note: As Carbonic acid is a diprotic acid, it plays a crucial component in the process of ocean acidification. It is used in the precipitation of many ammonium salts such as ammonium persulfate.