Give a chemical test to disintiguish between

1) Ammonium chloride and Sodium chloride

2) Sodium sulphate and Ammonium sulphate

In both the combination one is ammonium salt and other is sodium salt and anion is same so we treat the solution with NaOH.The ammonium salt will release the ammonia gas which can be smelled while sodium salt will not show any change. In first case NH₄Cl on treatment with NaOH give the smell of NH₃.In second case (NH₄)SO₄ on treatment with NaOH will give the smell of NH₃.Chemical reaction is shown below.

1) NaOH(aq) + NH₄Cl(aq) ==> NaCl(aq) + H₂O(l) + NH₃(g)

2) 2NaOH(aq) + (NH₄)₂SO₄(aq) ==> Na₂SO₄(aq) + 2H₂O(l) + 2NH₃(g)