Which of the following statement(s) is (are) correct with reference to the ferrous and ferric ions?

a. Fe^3+ gives brown colour with potassium ferricyanide.

b. Fe^2+ gives blue precipitate with potassium ferricyanide.

c. Fe^3+ gives red colour with potassium thiocyanate.

d. Fe^2+ gives brown colour with ammonium thiocyanate

(b,c) The blue precipitate of Fe^2+ ions with potassium ferricyanide is due to formation of Turnbull’s blue KFe^II [Fe^iii(CN) base 6]

Fe^2+ K base 3 [Fe(CN) base 6] ? K.Fe^ii [Fe^iii (CN) base 6] + 2K^+

Potassium ferro ferricyanide

The red colouration of Fe^3+ ions with potassium thiocyanate is due to the formation of [Fe(CNS) base 3]

Fe^2+ + 3KCNS ? [Fe(CNS) base 3] + 3K^+

(Ferric thiocyanate red colour)