How can you distinguish between
(i) `CO_(3)^(-2) and SO_(3)^(-2)` ions?
(ii) `NO_(3)^(-)` ion and `NO_(2)^(-)` ion ?

Explanation

(i) Sulphite ion `(SO_(3)^(-2))` will give `SO_(2)` gas which converts orange coloured `K_(2)Cr_(2)O_(7)` solution into green. Carbonate `(CO_(3)^(-2))` will give `CO_(2)` gas which do not given green colour with `K_(2)Cr_(2)O_(7)` solution.
(ii) `NO_(2)^(-)` gives brown `NO_(2)` gas with dil. and acid but `NO_(3)^(-)` does not.