(a) What is “baking powder”? How does it make the cake soft and spongy?(b) In addition to sodium hydrogencarbonate, baking powder contain a substance X. Name the substance. What is the role of substance X in the baking powder?

(a) Baking powder is a mixture of baking soda and tartaric acid. When mixed with water the sodium hydrogen carbonate(baking soda) reacts with tartaric acid, as a result, carbon dioxide gas is liberated. This carbon dioxide is trapped in wet dough and bubbles out slowly making the cake soft and spongy.

(b) Substance X is tartaric acid. Tartaric acid reacts with sodium carbonate formed and neutralises it. Otherwise, cakes and bread will taste bitter.