Analytical ChemistryHard
Question
Select the incorrect statement.
Options
A. Marsh′s test involves the reduction of soluble arsenic compound to arsine by nascent hydrogen in acidic solution and its subsequent decomposition into hydrogen and metallic arsenic as a brownish-black mirror on heating in a glass tube mixed with hydrogen.
B.Ammonical silver nitrate gives metallic silver mirror with saturated solution of hydrazine sulphate.
C.Red precipitate of silver (I) chromate is soluble in dilute nitric acid and ammonia solution.
D.None of these
Solution
(A) As3+ + 3Zn + 3H+ → AsH3↑ + 3Zn2+ ; 4AsH3 
4As ↓ + 6H2 ↑
(B) 4[Ag(NH3)2]+ + H2N - NH2.H2SO4 → 4Ag↓ + N2 ↑ + 6NH4+ + 2NH3 ↑ + SO42-
(C) 2Ag2CrO4 ↓ + 2H+ ⇋ 4Ag+ + Cr2O72- + H2O
Ag2CrO4 ↓ + 4NH3 ⇋ 2[Ag(NH3)2]+ + CrO42-
So, all statements are correct.
4As ↓ + 6H2 ↑(B) 4[Ag(NH3)2]+ + H2N - NH2.H2SO4 → 4Ag↓ + N2 ↑ + 6NH4+ + 2NH3 ↑ + SO42-
(C) 2Ag2CrO4 ↓ + 2H+ ⇋ 4Ag+ + Cr2O72- + H2O
Ag2CrO4 ↓ + 4NH3 ⇋ 2[Ag(NH3)2]+ + CrO42-
So, all statements are correct.
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