Write Lewis structures for \(\mathrm{CO}_{3}{ }^{2-}, \mathrm{HCO}_{3}{ }^{-}\), and \(\mathrm{H}_{2} \mathrm{CO}_{3}\). When acid is added to an aqueous solution containing carbonate or bicarbonate ions, carbon dioxide gas is formed. We generally say that carbonic acid \(\left(\mathrm{H}_{2} \mathrm{CO}_{3}ight)\) is unstable. Use bond energies to estimate \(\Delta H\) for the reaction (in the gas phase):

\[\mathrm{H}_{2} \mathrm{CO}_{3} \longrightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}\]

Specify a possible cause for the instability of carbonic acid.