WBCS Preliminary Examination 2023 — General Studies · Question 152 of 200

Answer: (C) sodium hydrogen carbonate and tartaric acid

PSC's answer is sodium hydrogen carbonate with tartaric acid. Strictly, that mixture is baking powder; baking soda by itself is just sodium hydrogen carbonate, $NaHCO_3$. When the powder is heated or moistened, the acid reacts with the hydrogen carbonate to release carbon dioxide, which makes cakes and bread rise, and the tartaric acid also neutralises the sodium carbonate that would otherwise leave a bitter taste. Options with sodium carbonate (washing soda is $Na_2CO_3\cdot10H_2O$) or acetic acid (vinegar) are wrong. $NaHCO_3$ is also an antacid and is used in soda-acid fire extinguishers; tartaric acid occurs in tamarind and grapes. Strictly, sodium hydrogen carbonate + tartaric acid is BAKING POWDER; baking soda is sodium hydrogen carbonate alone (NCERT Class X usage).