JAMB Chemistry 2022 Paper

Concept:Acids, especially carboxylic acids, react with carbonate or hydrogen carbonate salts to release carbon(IV) oxide gas.Explanation:Trioxocarbonate(IV) solution contains $\mathrm{CO}_3^{2-}$ or $\mathrm{HCO}_3^-$ ions.When a strong enough acid is added, it protonates these ions to form carbonic acid, $\mathrm{H}_2\mathrm{CO}_3$.Carbonic acid is unstable and decomposes to give carbon(IV) oxide gas, $\mathrm{CO}_2$, and water.Among the options, only $\mathrm{CH}_3\mathrm{COOH}$ is a carboxylic acid.It reacts with $\mathrm{NaHCO}_3$ solution as follows:$$\mathrm{CH}_3\mathrm{COOH} + \mathrm{NaHCO}_3 \rightarrow \mathrm{CH}_3\mathrm{COONa} + \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2 \uparrow$$Ethanol, $\mathrm{C}_2\mathrm{H}_5\mathrm{OH}$, is neutral and does not liberate $\mathrm{CO}_2$.The hydrocarbons $\mathrm{C}_3\mathrm{H}_4$ and $\mathrm{C}_6\mathrm{H}_6$ are also unreactive with carbonate solutions.Therefore, the compound likely to liberate carbon(IV) oxide is ethanoic acid.Answer:D. $\mathrm{CH}_3\mathrm{COOH}$