Question

The brown complex obtained in the detection of nitrate radical is formulated as $\left[Fe\right(H_{2}O{)}_{5}NO]S{O}_4$. What is the oxidation number of Fe in this complex?

• A. 1
• B. 2
• C. 3
• D. 0

Answer 1

Answer: (A)

1

Brown ring test is a confirmatory test for nitrate.

When an aqueous solution of a nitrate salt is treated with ferrous sulphate and conc. sulphuric acid, a brown ring is formed at the junction of two liquids.

We know that,

Charge on $S{O}_4^{2-}=-2$

Overall charge on complex is $+2$ and charge on $NO=+1$.

Let the charge on $Fe$ be $x$,

So,

$x+1=+2$

$x=+1$

Therefore, the oxidation number of $Fe$ in given complex is $+1$.

Hence, the correct option is (A).