Analytical ChemistryHard
Question
Select the correct statements with respect to the manganese nitrate solution in water.
Options
A.It gives pink precipitate of Mn(NH4)PO4.7H2O with Na2HPO4, in the presence of ammonia solution.
B.It gives white precipitate of Mn(OH)2 with sodium hydroxide which rapidly oxidises on exposure to air, becoming brown.
C.On boiling with PbO2 and concentrated HNO3, a violet-red coloured product is obtained.
D.It gives white precipitate of manganese(II) sulphide with ammonium sulphide solution.
Solution
(A) Mn2+ + NH3 + HPO42- → Mn(NH4)PO4 ↓ (pink)
(B) Mn2+ + 2OH- → Mn(OH)2 ↑ (white)
2Mn(OH)2 + O2 → 2MnO (OH)2↑ (brown)
(C) 5PbO2 + 2Mn2+ + 4H+ → 2MnO4- + 5Pb2+ + 2H2O
(D) Mn2+ + S2- → MnS ↓ (pink)
(B) Mn2+ + 2OH- → Mn(OH)2 ↑ (white)
2Mn(OH)2 + O2 → 2MnO (OH)2↑ (brown)
(C) 5PbO2 + 2Mn2+ + 4H+ → 2MnO4- + 5Pb2+ + 2H2O
(D) Mn2+ + S2- → MnS ↓ (pink)
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