Question

Which one of the following complexes is violet in colour?

• A. $\left[ Fe ( CN )_{6}\right]^{4}$
• B. $\left[ Fe ( SCN )_{6}\right]^{4}$
• C. $Fe _{4}\left[ Fe \left( CN _{6}\right)\right]_{3} \cdot H _{2} O$
• D. $\left[ Fe ( CN )_{5} NOS \right]^{4}$

Answer 1

Answer: (D)

(1) $\left[ Fe ( CN )_{6}\right]^{4-} \rightarrow$ Pale yellow solution
(2) $\left[ Fe ( SCN )_{6}\right]^{4-} \rightarrow$ Blood red colour
(3) $Fe _{4}\left[ Fe \left( CN _{6}\right)\right]_{3} \cdot H _{2} O \rightarrow$ Prussian blue
(4) $\left[ Fe ( CN )_{5} NOS \right]^{4-} \rightarrow$ Violet colour