Analytical ChemistryHard
Question
Which of the following compound(s) is /are insoluble in excess aqueous sodium hydroxide ?
Options
A.ZnCl2
B.CdCl2
C.AlCl3
D.MnCl2
Solution
(B) Cd2+ + 2OH- → Cd(OH)2 ↓ (white). ; Cd(OH)2 is insoluble in excess reagent.
(D) Mn2+ + 2OH → Mn(OH2) ↓ (white) ; Mn(OH)2 is insoluble in excess reagent but precipitate turns to brown slowly on exposure to air forming hydrated manganese dioxide. ;
2Mn(OH)2↑ + O2 → 2MnO(OH)2 ↓ (brown).
(D) Mn2+ + 2OH → Mn(OH2) ↓ (white) ; Mn(OH)2 is insoluble in excess reagent but precipitate turns to brown slowly on exposure to air forming hydrated manganese dioxide. ;
2Mn(OH)2↑ + O2 → 2MnO(OH)2 ↓ (brown).
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