Question

Prussian blue is formed when
A. ferrous sulphate reacts with `FeCl_(3)`
B. ferric sulphate reacts with `Na_(4)[Fe(CN)_(6)]`
C. ferrous ammonium sulphate reacts with `FeCl_(3)`
D. ammonium sulphate reacts with `FeCl_(3)`

Answer 1

Correct Answer - B
When the sodium fusion extract is added with `FeCl_(3)` and then the resulting solution is acidified with dilute hydrochloric acid , the appearance of Prussian blue colouration confirms the presence of nitrogen in the organic compound.
`Na + C + N to NaCN `
`FeSO_(4) + 2NaCN to Fe(CN)_(2) + Na_(2)SO_(4)`
`Fe(CN)_(2) + 4NaCN to Na_(4) [Fe(CN)_(6)]`
`3 Na_(4)[Fe(CN)_(6)] + 4FeCl_(3) to underset("Prussian blue")(Fe_(4)[Fe(CN)_(6)]_(3)) + 12 NaCl`