What is formed when bicarbonate ions react with excess hydrogen ions in the bicarbonate buffer system?

In the bicarbonate buffer system, when bicarbonate ions (HCO₃⁻) react with excess hydrogen ions (H⁺), they form carbonic acid (H₂CO₃). This reaction is crucial in maintaining the pH balance within the blood and other bodily fluids.

The process can be summarized by the reaction:

HCO₃⁻ + H⁺ ↔ H₂CO₃.

Carbonic acid is a weak acid that can dissociate into water and carbon dioxide, which is then exhaled through the lungs. This buffering mechanism helps to counteract changes in acidity, stabilizing the pH of blood.

Other compounds listed do not form from the interaction of bicarbonate ions and excess hydrogen ions in this context. Sodium bicarbonate is a form of bicarbonate itself, while lactic acid and acetic acid are products of different metabolic pathways unrelated to this particular buffering system.