Analytical ChemistryHard
Question
A metal nitrate solution reacts with dilute hydrochloric acid to give a white precipitate which is soluble in concentrated potassium chloride. White precipitate on passing of hydrogen sulphide gas is converted into black precipitate. The black precipitate on boiling with hydrogen peroxide (3%) is converted again to a white precipitate which is soluble in ammonium acetate. The cation of the metal nitrate is :
Options
A.Pb2+
B.Ag+
C.Hg2+
D.Bi3+
Solution
Pb2+ + 2Cl- → PbCl2↓ (white) ; PbCl2 + 2Cl- → [PbCl4]2- (colourless soluble complex)
PbCl2↓ + H2S → PbS↓ (black) + 2HCl
PbS + 4H2O2 → PbSO4↓ (white) + 4H2O
PbSO4↓ + 2CH3COONH4 → (NH4)2SO4 + (CH3COO)2Pb
PbCl2↓ + H2S → PbS↓ (black) + 2HCl
PbS + 4H2O2 → PbSO4↓ (white) + 4H2O
PbSO4↓ + 2CH3COONH4 → (NH4)2SO4 + (CH3COO)2Pb
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