Question

How would you distinguish between baking powder and washing soda by heating ?

Answer 1

Baking powder (NaHCO₃) on heating produces carbon dioxide which extinguishes a burning matchstick. It also gives sodium carbonate and water vapour.

2NaHCO₃ + Heat → Na₂CO₃ + CO₂ + H₂O

When washing soda (Na₂CO₃. 10 H₂O) is heated it does not produce carbon dioxide but it loses water of Crystallisation molecules.

NaCO₃ .10H₂O+Heat → Na₂CO₃ + 10 H₂O

Answer 2

On heating NaOH₃(baking soda), CO₂(carbon dioxide) gas is given out that turns limewater milky

\(2NaHCO_3(s)\overset{\triangle}{\longrightarrow} \) Na₂CO₃(s) + H₂O(l) + CO₂(g)

While on heating Na₂CO₃.10H₂O (washing soda) water of crystallization is given out and the salt becomes anhydrous. The presence of water of crystallization given as product can be tested by treating. it with anhydrous CuSO₄ (white) which becomes blue in colour in its contact.

Na₂CO₃.10H₂O \(\overset{\triangle}{\longrightarrow}\)Na₂CO₃ + 10H₂O