Chemistry - Redox Reactions Question with Solution | TestHub

In [$\mathrm{Fe}(\mathrm{CN}{)}_5\mathrm{NO}{]}^{2-}$, $\mathrm{NO}$ is $\mathrm{N}{\mathrm{O}}^{+}$: $x$ - 5 + 1 = -2 $\Rightarrow$ $x$ = +2. Sulphide adds to the nitrosyl ligand to give [$\mathrm{Fe}(\mathrm{CN}{)}_5(\mathrm{NOS}){]}^{4-}$; the oxidation state of Fe stays +2. Hence (d).