Which of the following is the chemical formula for the conjugate acid of the carbonate ion, CO_3^{2-}?

• A. CO_3^{2-}
• B. CO_2
• C. H_2CO_3
• D. HCO_3^{-}

Answer: (D)

Verified step by step guidance

1. Understand that a conjugate acid is formed when a base gains a proton (H\^+). In this case, the base is the carbonate ion, CO\_3\^{2-}.
2. Write the chemical formula of the base: CO\_3\^{2-}. When it gains one proton (H\^+), the charge will increase by +1, because a proton has a +1 charge.
3. Add one hydrogen ion (H\^+) to the carbonate ion to form the conjugate acid. This gives the formula HCO\_3\^{-}, where the charge is now -1.
4. Recognize that HCO\_3\^{-} is called the bicarbonate ion, which is the conjugate acid of the carbonate ion.
5. Confirm that the other options (CO\_3\^{2-}, CO\_2, H\_2CO\_3) do not represent the conjugate acid formed by adding a single proton to CO\_3\^{2-}.