Na2CO3 reacts with HCl in the chemical equation: Na2CO3(s) + 2 HCl(aq) = CO2(g) + H2O(l) + 2 NaCl(aq). One molecule of Na2CO3 (sodium carbonate) combines with two molecules of hydrochloric acid (HCl) to produce one molecule each of carbon dioxide and water, plus two molecules of sodium chloride.
In this experiment, small amounts of the salt (Na2CO3) are added into an aqueous solution of hydrochloric acid (HCl). The reaction is spontaneous and exothermic, because it occurs between a strong acid, namely HCl, and Na2CO3, which acts as a base in this situation. Na2CO3 can be either an acid or a base depending on the solution: In solutions with a strong base, it acts as an acid, and in solutions with a strong acid, it acts as a base. The energy produced in this reaction is in the form of heat.