How to distinguish between sodium carbonate and sodium sulphate using a reagent?
Answers
(1) Sodium carbonate gives a white precipitate of magnesium carbonate on mixing with magnesium sulphate solution.
Na2CO3 (aq) + MgSO4 (aq) = MgCO3 (s) + Na2SO4 (aq)
Sodium bicarbonate does form a precipitate with MgSO4 solution as magnesium bicarbonate is soluble in water.
Instead of MgSO4 solution, a solution of MgCl2 or CaCl2 can also be used. The results will be similar.
(2) On heating, sodium bicarbonte easily decomposes to give carbon dioxide, which turns lime water milky.
2NaHCO3 = Na2CO3 + CO2 + H2O
Na2CO3 does not decompose even at moderately high temperatures.
Sodium carbonate gives a white precipitate of magnesium carbonate on mixing with magnesium sulphate solution. Sodium bicarbonate does form a precipitate with MgSO4 solution as magnesium bicarbonate is soluble in water. Instead of MgSO4 solution, a solution of MgCl2 or CaCl2 can also be used.