Solution of alkali metal cyanide containing freshly prepared ion `(II)` sulphate solution and dilute `H_(2)SO_(4)` on exposure to air produces prussian blue precipitate

Answer

1

Explanation

`Fe^(2+)+2 CN^(-) toFe(CN)_(2)darr,Fe(CN)_(2)darr+4CN^(-)to[Fe(CN)_(6)]^(4-)`
`4Fe^(2+)+O_(2)+4H^(+)to4Fe^(3+)+2H_(2)O,Fe^(3)+[Fe(CN)_(6)]^(4-)toFe_(4)[Fe(CN)_(6)]_(3)darr`