Sodium bicarbonate (baking soda, NaHCO3) is used in bakery products as a leavening agent. When heated, it decomposes according to the reaction: 2NaHCO3(s) → Na2CO3(s) + H2O(g) + CO2(g). The gaseous products, water vapour and especially carbon dioxide, are trapped within the dough, causing it to expand and become light and porous. Carbon dioxide is the primary gas responsible for the leavening action.