Question

why we use baking powder in cake instead of baking soda? ?

Answer 1

Baking powder has acid powder mixed with it.Wheareas baking soda needs acid to start action.More importantly baking powder can be eaten but baking soda can't be eaten.So,we use baking powder in cake.

Answer 2

Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid and is used for increasing the volume and lightening the texture of baked goods. Baking powder works by releasing carbon dioxide gas into a batter or dough through an acid-base reaction, causing bubbles in the wet mixture to expand and thus leavening the mixture


Actually baking powder is mainly just baking soda( sodium bicarbonate) mixed with an acid i.e mainly tartaric acid .
The reaction is
Baking soda + tartaric acid :-) sodium tartarate + water + carbon-dioxide.
Also tartaric acid neutralises the metallic taste that's come from the batter or dough and also adds sweetness to it.

Remember,
Baking soda need an acid. Baking powder has an acid.

I hope this helps!!!