In an aqueous solution, which process could cause the concentration of CO3^{2-} to decrease while the dissolved inorganic carbon (DIC) increases?

• A. Addition of a base, increasing CO3^{2-} concentration
• B. Precipitation of CaCO3, removing both CO3^{2-} and DIC
• C. Addition of a strong acid, converting CO3^{2-} to HCO3^{-}
• D. Evaporation of water, concentrating all ions equally

Answer: (C)

Verified step by step guidance

1. Understand the species involved: CO3^{2-} (carbonate ion) and DIC (dissolved inorganic carbon), which includes CO2, H2CO3, HCO3^{-}, and CO3^{2-}.
2. Recognize that adding a strong acid increases H^{+} concentration, which shifts the carbonate equilibrium toward bicarbonate (HCO3^{-}) by protonating CO3^{2-}.
3. Write the relevant equilibrium reaction: \(\mathrm{CO3^{2-} + H^{+} \rightleftharpoons HCO3^{-}}\).
4. Note that converting CO3^{2-} to HCO3^{-} decreases the concentration of CO3^{2-} but increases the total dissolved inorganic carbon (DIC), since HCO3^{-} is part of DIC.
5. Contrast this with other processes: addition of base increases CO3^{2-}, precipitation removes both CO3^{2-} and DIC, and evaporation concentrates all species equally without changing their relative amounts.