When sodium carbonate reacts with an excess of sulfur dioxide, it undergoes a chemical reaction to form sodium hydrogen sulfite and sodium bisulfite. The reaction can be represented as follows:

Na2CO3 + 2SO2 + H2O → 2NaHSO3 + NaHCO3

In this reaction, sulfur dioxide (SO2) acts as an acidic gas and reacts with water (H2O) to form sulfurous acid (H2SO3). The sulfurous acid then reacts with sodium carbonate (Na2CO3) to produce sodium hydrogen sulfite (NaHSO3) and sodium bicarbonate (NaHCO3).

The products of this reaction are sodium hydrogen sulfite and sodium bicarbonate. Sodium hydrogen sulfite is a white crystalline compound that is soluble in water and has a slightly acidic taste. It is used as a reducing agent, an antioxidant, and a preservative in the food industry. Sodium bicarbonate, also known as baking soda, is a white, crystalline powder that is soluble in water and has a slightly alkaline taste. It is commonly used as a leavening agent in baking, as well as in various household cleaning products.