Distinguish between the following substances.

a) Add aqueous chlorine solution ( or any other aqueous solutions of halogens ) to the two samples. The one which turns aqueous chlorine solution from pale green to colourless is sodium sulphite. It is due to a redox reaction.

Cl2 + ( 2e- ) ---> (2Cl-) ***** ( reduction )

( SO3 2- ) + H2O ---> ( SO4 2- ) + ( 2H+ ) + ( 2e- ) ***** ( oxidation )

Overall equation : Cl2 + ( SO3 2- ) + H2O ---> (2Cl-) + ( SO4 2- ) + ( 2H+ )

b) Heat the two oxides with carbon and the one which gives out carbon dioxide is zinc oxide.

2ZnO + C ---> 2Zn + CO2

c) Test the two solutions with aqueous sodium hydroxide. The one which gives a jelly-like white precipitate is zinc nitrate solution.

Zn + ( 2OH-) ---> Zn(OH)2

d) Warm the two solutions with aqueous sodium hydroxide solution. The one which gives a fishy smell is ammonium sulphate solution.

( NH4+) + (OH-) ---> NH3 + H2O

Hope it helps.