Question

`K_(4)[Fe(CN)_(6)]` is used to detect
A. `Cu^(2+)`
B. `As^(3+)`
C. `Zn^(2+)`
D. `Fe^(3+)`

Answer 1

Correct Answer - A::C::D
(a) `2Cu^(2+)+K_(4)[Fe(CN)_(6)] rarr underset("(chocolate brown ppt.)")(Cu_(2)[Fe(CN)_(6)])+4K^(+)`
(b) Is not possible because `As^(3+)` does not react with `K_(4)[Fe(CN)_(6)]`
(c ) `2Zn^(2+)+K_(4)[Fe(CN)_(6)] rarr underset("(bluish white ppt.)")(Zn_(2)[Fe(CN)_(6)])+4K^(+)`
(d ) `4Fe^(3+)+3K_(4)[Fe(CN)_(6)] rarr underset("(Prussian blue)")(Fe_(4)[Fe(CN)_(6)]_(3))=12K^(+)`