What is the composition of baking powder? Explain how it bakes the bread to make it spongy? (with chemical equations)

PLACEHOLDER ANSWER - the answer is an explanation with equations. Baking powder is a mixture of sodium bicarbonate, a mild edible acid such as tartaric acid, and starch to keep it dry. When moistened and heated, $$\text{NaHCO}_3 + \text{H}^+ \rightarrow \text{Na}^+ + \text{H}_2\text{O} + \text{CO}_2$$, and on heating $$2\text{NaHCO}_3 \rightarrow \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} + \text{CO}_2$$. The $$\text{CO}_2$$ bubbles are trapped in the dough and expand on heating, making the bread soft and spongy, while the acid removes the bitter-tasting $$\text{Na}_2\text{CO}_3$$.