$F{e}^{2+}\left(aq\right)+N{O}_3{}^{-}\left(aq\right)+H_{2}S{O}_4\left(conc\right)⟶$ Brown ring.
The oxidation number of iron in brown ring complex is:

Q. Oxidation number of iron in brown ring complex (obtained in ring-test of ${NO}_3^{-}$) is ?
Brown ring complex: ${\left[Fe{\left(H_{2}O\right)}_{5}NO\right]}^{2+}$

Q. In the ring test of $N{O}_3^{-}$ ion, $F{e}^{2+}$ ion reduces nitrate ion to nitric oxide, which combines with $F{e}^{2+}\left(aq\right)$ ion to form a brown complex. Write the reaction involved in the formation of brown ring

Q. The brown ring complex compound is formulated as $\left[Fe\right(H_{2}O{)}_5\left(NO\right)]S{O}_4$]. The oxidation state of iron in this complex is:

Q. In the brown ring complex, the oxidation state of iron is:

Q. The brown ring complex compound is formulated as $\left[Fe{\left(H_{2}O\right)}_{5}NO\right]{SO}_4$. The oxidation state of iron is