`K_(4)[Fe(CN)_(6)]` can be used to detect one or more out of `Fe^(2+),Fe^(3+),Zn^(2+),Cu^(2+),Cd^(2+)`

Options

A. `Fe^(2+),Fe^(3+)` only
B. `Fe^(3+), Zn^(2+), Cu^(2+)` only
C. All but not `Ca^(2+)`
D. All

Answer

D

Explanation

`Fe^(2+)+2K^(+)[Fe(CN)_6]darr` (white) (in absence of air)
`Fe^(3+)+[Fe(CN)_6]^(4-)toFe_4[Fe(CN)_6]_3`(prussian blue precipitate or solution)
`Zn^(2+)+2K^(+)[Fe(CN)_6]^(4-)`(excess)`toK_2Zn_3[Fe(CN)_6]_2darr`(bluish -white/white)
`Ca^(2+)+2K^(+)[Fe(CN)_6]^(4-)toK_2Ca[Fe(CN)_6]darr`(white)
`Cu^(+)+2K^(+)+[Fe(CN)_6]^(4-)toCu_2[Fe(CN)_6]darr` [chocolate brown]