A strong acid is a carbonic acid, not carbonic acid itself. Weak acids such as H ₂ CO ₃ are dissociated into proton-containing cations (H ⁺ cations) and bicarbonate-containing anion-forming cations (HCO ₃ ^– cations). The compound does not completely dissociate in water. As a matter of fact, the bicarbonate ion of carbonic acid, which is the conjugate base of carbonic acid, is a relatively good base. Due to these reasons, carbonic acid is classified as a weak acid rather than as a strong acid.