JEE Main 2022 · 29 June · evening · Single correct · +4 / −1
Amongst baking soda, caustic soda and washing soda, carbonate anion is present in :
- (a) washing soda only.
- (b) washing soda and caustic soda only.
- (c) washing soda and baking soda only.
- (d) baking soda, caustic soda and washing soda.
Answer and solution
Answer (a) washing soda only.
Solution
Chemistry ma’am · 3 steps
Write the formula of each soda first; only one of them has a bare CO₃²⁻ ion in it.
- Match the names. Baking soda is sodium hydrogencarbonate, caustic soda is sodium hydroxide, and washing soda is sodium carbonate decahydrate.
Common name Formula Anion present Baking soda NaHCO₃ HCO₃⁻ (hydrogencarbonate) Caustic soda NaOH OH⁻ (hydroxide) Washing soda Na₂CO₃.10H₂O CO₃²⁻ (carbonate) - Carbonate versus bicarbonate. The carbonate anion is CO₃²⁻. Baking soda carries HCO₃⁻, a different ion with one hydrogen and a single negative charge. Caustic soda has no carbon at all.
- So. Only washing soda contains the carbonate anion, which is option (a).
The idea to keep. Baking soda is NaHCO₃, washing soda is Na₂CO₃.10H₂O, caustic soda is NaOH. Hydrogencarbonate and carbonate are different anions, so read the question's ion name carefully.
Answer from the NTA final answer key. Solution by PrepWiser.