Baking soda has a pH of 8.3. This compound, also called sodium bicarbonate, is made up of sodium, hydrogen, carbon and oxygen. Baking soda is classified as a weak base, which means it does not completely ionize in water.
Manufacturers produce baking powder by mixing baking soda and cream of tartar. When the two ingredients are dry, they do not react with each other. When a baker adds liquid to the baking powder, however, the baking soda and cream of tartar enter into a chemical reaction. This reaction produces carbon dioxide gas, which is what makes baked goods rise. This is an example of a weak base reacting with a weak acid, according to C.R. Nave of Georgia State University.