Which of the following is called baking soda?

The correct answer is Option (2) → \(\ce{NaHCO3}\)

Baking soda is sodium hydrogen carbonate (sodium bicarbonate), \(\ce{NaHCO3}\). When it is heated in a dough or batter it gives off carbon dioxide, and the gas bubbles make cakes and breads soft and spongy:

• \(\ce{2NaHCO3 -> Na2CO3 + H2O + CO2}\)

Being a mild base, it is also used in antacids to relieve acidity.

Tip: Baking soda (\(\ce{NaHCO3}\)) and washing soda (\(\ce{Na2CO3.10H2O}\)) are often mixed up. The “H” of hydrogen carbonate is what sets baking soda apart.