The balanced chemical equation for the reaction between carbonic acid (H₂CO₃) and sodium hydroxide (NaOH) is:
\[ \text{H}_2\text{CO}_3 (aq) + 2 \text{NaOH} (aq) \rightarrow \text{Na}_2\text{CO}_3 (aq) + 2 \text{H}_2\text{O} (l) \]
In this reaction, carbonic acid reacts with sodium hydroxide to produce sodium carbonate and water.