When you are baking, you will see recipes that call for baking power, baking soda, or both. But, are they interchangeable? What is their job in the recipe?
Recipes that call for both baking powder and baking soda contain some sort of acid (yogurt, brown sugar, etc), however the carbon dioxide created from the acid and baking soda is not enough to leaven the volume of batter in the recipe.
That’s why baking powder is used as well– to add necessary lift. This is important when you need more leavening than you have acid available in the recipe. This keeps it balanced.