Final answer:
A buffer solution of carbonic acid and bicarbonate reacts with added acids or bases to stabilize pH, involving bicarbonate reacting as either an acid or a base with water. The bicarbonate-carbonic acid system is particularly important in biological systems like blood, helping to maintain stable pH levels.
Step-by-step explanation:
A buffer solution of carbonic acid (H₂CO₃) and bicarbonate (HCO₃⁻) maintains pH stability by reacting with added acids or bases. The general buffer reaction can be given by two reversible reactions. When bicarbonate acts as an acid, it reacts with water as a base, producing carbonic acid and hydroxide ions:
HCO₃⁻(aq) + H₂O(l) ↔ H₂CO₃(aq) + OH⁻(aq)
Conversely, when bicarbonate acts as a base, it reacts with a hydronium ion, coming from an acid like HCl, forming carbonic acid and water:
H₃O⁻(aq) + HCO₃⁻(aq) ↔ H₂CO₃(aq) + H₂O(l)
In biological systems such as blood, the bicarbonate buffer system is crucial. The presence of carbon dioxide (CO₂), bicarbonate ion (HCO₃⁻), and carbonic acid (H₂CO₃) helps to regulate pH levels by removing excess hydrogen ions and moderating pH changes.