Acids are substances that dissolve in water to generate an excess of H+ ions. They react with bases to produce a salt and water. With metal carbonates, products include a salt of that metal (depending on the acid and metal), water and carbon dioxide. For example:Sodium carbonate (NaCO3) + Hydrogen Chloride (HCl) -> Sodium chloride (NaCl) + water (H2O) + carbon dioxide (CO2))Thus, observations in this reaction include bubbling from the release of CO2. When collected, the gas turns lime water milky.