Chocolate brown precipitate is formed with:

Options

A. `Cu^(2+)` ions and `[Fe(CN)_(6)]^(3-)`
B. `Cu^(2+)` ions and `[Fe(CN)_(6)]^(4-)`
C. `Fe^(2+)` ions and `[Fe(CN)_(6)]^(4-)`
D. `Fe^(2+)` ions and dimethylglyoxime (in ammonical solution)

Answer

B

Explanation

(a) `Cu^(2+) overset([Fe(CN)_(6)]^(3-))rarr underset(("Green ppt"))(Cu_(3)[Fe(CN)_(6)I_(2)darr)`
(b)` underset(("Chocolate brown ppt"))(Cu_(2)[Fe(CN)_(6)])darr`
(c) `underset(("Pale blue in presence of" O_(2)))(K_(2)Fe[Fe(CN)]_(6)darr("White ppt"))`
(d) Red colouration