Question

Why is baking soda not preferred for baking purposes and instead baking powder is used?

Answer 1

Here is your answer:

Baking powder is baking soda (sodium bicarbonate) already mixed with an acid (usually cream of tartar). Therefore, baking powder on its own is used in baked goods that do not already contain an acid. It works in the same way baking soda does, by creating air bubbles which cause the batter to rise.