Which ion is hydrogen carbonate?

Which ion is hydrogen carbonate?

• A. CO3^2-
• B. HCO3-
• C. H2CO3
• D. H2CO4-

Answer: (B)

Hydrogen carbonate is the ion that forms when carbonic acid loses one proton. In water, carbonic acid (H2CO3) can dissociate to give HCO3−: H2CO3 ⇌ H+ + HCO3−. The bicarbonate ion carries a single negative charge, so it is named hydrogen carbonate. The carbonate ion CO3^2− has no hydrogens and comes from further loss of a proton: HCO3− ⇌ H+ + CO3^2−, while the neutral molecule H2CO3 is not an ion. A species like H2CO4− doesn’t exist under ordinary conditions.

Hydrogen carbonate is the ion that forms when carbonic acid loses one proton. In water, carbonic acid (H2CO3) can dissociate to give HCO3−: H2CO3 ⇌ H+ + HCO3−. The bicarbonate ion carries a single negative charge, so it is named hydrogen carbonate. The carbonate ion CO3^2− has no hydrogens and comes from further loss of a proton: HCO3− ⇌ H+ + CO3^2−, while the neutral molecule H2CO3 is not an ion. A species like H2CO4− doesn’t exist under ordinary conditions.