Which of the following is used in making baking soda?
- ASodium carbonate
- BBleaching powder
- CSodium hydroxide
- DNone of the above
Show answer and explanation
Correct answer: (a) Sodium carbonate
Explanation
Baking soda is sodium bicarbonate (sodium hydrogen carbonate, NaHCO₃). It is made by passing carbon dioxide into a solution of sodium carbonate:
- Na₂CO₃ + H₂O + CO₂ → 2NaHCO₃
On a large scale it comes from the Solvay process, in which brine (NaCl), ammonia and carbon dioxide react and sodium bicarbonate settles out.
Bleaching powder (CaOCl₂) is a disinfectant and sodium hydroxide (caustic soda) a strong alkali; neither is used to make baking soda.