Question

During the formation of ferric thiocyanate and potassium nitrate from ferric nitrate and potassium thiocyanate, the red color is due to the formation of

• A. $Fe(CNS{)}_2^{+}$
• B. $Fe(CNS{)}^{2+}$
• C. $Fe(CNS{)}_3$
• D. $Fe(CNS{)}^{2-}$

Answer 1

The correct option is B

$Fe(CNS{)}^{2+}$

Ferric thiocyanate is formed three stages. The steps are given below:

$F{e}^{3+}+CN{S}^{-}\leftrightharpoons Fe(CNS{)}^{2+}$

$Fe(CNS{)}^{2+}+CN{S}^{-}\leftrightharpoons Fe(CNS{)}_2^{+}$

$Fe(CNS{)}_2^{+}+CN{S}^{-}\leftrightharpoons Fe(CNS{)}_3$

Among these, $Fe(CNS{)}^{2+}$ is responsible for deep red colour.