Question

Which one of the following complexes is violet in colour ?

• A. $F{e}_4\left[Fe\right(CN{)}_6{]}_3.H_{2}O$
• B. $\left[Fe\right(CN{)}_6{]}^{4-}$
• C. $\left[Fe\right(CN{)}_{5}NOS{]}^{4-}$
• D. $\left[Fe\right(SCN{)}_6{]}^{4-}$

Answer 1

The correct option is C $\left[Fe\right(CN{)}_{5}NOS{]}^{4-}$

$\left[Fe\right(CN{)}_6{]}^{4-}$ - Plate yellow
$\left[Fe\right(CN{)}_6{]}^{3-}$ - Yellow
$Fe(SCN{)}_3$ - Red colouration
$\left[Fe\right(CN{)}_5\left(NOS\right){]}^{4-}$ - Violet colour

$N{a}_{2}S+\underset{\text{sodium nitroprusside}}{N{a}_2\left[Fe\right(CN{)}_{5}NO]}\to \underset{\text{sodium thionitroprusside (violet)}}{N{a}_4\left[Fe\right(CN{)}_{5}NOS]}$
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