Question

When $SC{N}^{-}$ is added to an aqueous solution containing $Fe(N{O}_3{)}_3$ ,the complex ion produced is

• A. $[Fe(O{H}_2{)}_2(SCN){]}^{2+}$
• B. $[Fe(O{H}_2{)}_5(SCN){]}^{2+}$
• C. $[Fe(O{H}_2{)}_8(SCN){]}^{2+}$
• D. $[Fe(O{H}_2)(SCN){]}^{6+}$

Answer 1

Answer: (B)

On adding $SC{N}^{-}$ to an aqueous solution of $Fe(N{O}_3{)}_3$, a blood red colour, due to the formation of $[Fe(H_{2}O{)}_5(SCN){]}^{2+}$ complex, is obtained. This test is used for the detection of $F{e}^{3+}$ ion.
$SC{N}^{-}+Fe(N{O}_3{)}_3+H_{2}O\to \underset{\text{blood red colour}}{[Fe(O{H}_2{)}_5(SCN){]}^{2+}}+N{O}_3^{-}$