When metal carbonates and metal hydrogen carbonates react with acids, it forms

When metal carbonate/metal hydrogen carbonate reacts with acid they produce salt along with carbon dioxide and water. The molecular formula of metal carbonates contain ${\mathit{CO}}_3^{2-}$ ions. 

For example the reaction of sodium carbonate and hydrochloric acid is
$N{a}_{2}C{O}_3+2\mathit{HCl}\to 2\mathit{NaCl}+H_{2}O+C{O}_2$