Analytical ChemistryHard
Question
A coloured solution of a salt gives following reactions.
(i) It gives white precipitate with sodium hydroxide which becomes brown on exposure to air.
(ii) It gives white precipitate with ammonia solution which is soluble in ammonium salts.
(iii) Its acidified solution containing a few drops of dilute AgNO3 on boiling with ammonium peroxodisulphate gives a reddish violet solution. The cation of the salt is :
(i) It gives white precipitate with sodium hydroxide which becomes brown on exposure to air.
(ii) It gives white precipitate with ammonia solution which is soluble in ammonium salts.
(iii) Its acidified solution containing a few drops of dilute AgNO3 on boiling with ammonium peroxodisulphate gives a reddish violet solution. The cation of the salt is :
Options
A. Mn2+
B.Zn2+
C.Al3+
D.Ni2+
Solution
(i) Mn2+ + 2OH- → 2Mn(OH)2↓ (white)
2Mn(OH)2↓+ O2 → MnO(OH)2↓ (brown)
(ii) Mn2+ + 2NH3 + 2H2O ⇋ Mn(OH)2↓ + 2NH4+
with NH4+ the reaction proceeds towards the left.
(iii) 2Mn2+ + 5S2O82- → 2MnO4- + 10SO42- + 16H+
2Mn(OH)2↓+ O2 → MnO(OH)2↓ (brown)
(ii) Mn2+ + 2NH3 + 2H2O ⇋ Mn(OH)2↓ + 2NH4+
with NH4+ the reaction proceeds towards the left.
(iii) 2Mn2+ + 5S2O82- → 2MnO4- + 10SO42- + 16H+
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