The main components of baking powder are sodium bicarbonate (NaHCO3) and acidic substances (such as tartaric acid). They react in a humid environment to produce carbon dioxide gas, which promotes the fermentation and expansion of dough.

The following is the chemical equation of this reaction:

NaHCO3+H+→Na++H2O+CO2

Simplified version:

NaHCO3→Na++H2O+CO2