Baking powder and baking soda are two different things baking soda is pure sodium bicarbonate (NaHCO3) Baking powder -It contains sodium bicarbonate, but it includes the acidifying agent already (cream of tartar), and also a drying agent (usually starch). They are added to baked goods before cooking to produce carbon dioxide and cause them to 'rise'. Baking powder contains baking soda, but the two substances are used under different conditions.