Is CO₂ an acid or a base?

Carbon dioxide (CO₂) is an acidic oxide because it forms carbonic acid (H₂CO₃) when dissolved in water.

CO₂ reacts with water to form H₂CO₃ → H⁺ + HCO₃⁻. This releases hydrogen ions, showing acidic behavior. Non-metal oxides like CO₂, SO₂, and P₂O₅ are usually acidic. They react with bases to form salts, for example CO₂ + 2NaOH → Na₂CO₃ + H₂O. Hence, CO₂ is not a base; it does not accept protons or neutralize acids directly.

It’s an example of an acidic oxide important in environmental chemistry (acid rain, ocean acidification). Understanding CO₂’s acidic nature helps explain buffering in blood and the carbon cycle.