When an acid reacts with a carbonate, it forms a salt, water, and carbon dioxide gas. The general equation for this reaction is:

$$\text{Acid} + \text{Carbonate} \rightarrow \text{Salt} + \text{Water} + \text{Carbon Dioxide}$$

For example, when hydrochloric acid (HCl) reacts with sodium carbonate (Na2CO3), it forms sodium chloride (NaCl), water (H2O), and carbon dioxide gas (CO2). The balanced chemical equation for this reaction is:

$$2\text{HCl} + \text{Na}_2\text{CO}_3 \rightarrow 2\text{NaCl} + \text{H}_2\text{O} + \text{CO}_2$$