Chemistry - Redox Reactions Question with Solution | TestHub

(b) C is +4 in both $\mathrm{C}{\mathrm{O}}_3^{2-}$ and $\mathrm{HC}{\mathrm{O}}_3^{-}$ (protonation only) - non-redox. (c) Cr is +6 in both $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}$ and $\mathrm{Cr}{\mathrm{O}}_4^{2-}$ - non-redox. (d) P is +5 in both $\mathrm{HP}{\mathrm{O}}_4^{2-}$ and ${\mathrm{P}}_2{\mathrm{O}}_7^{4-}$ (condensation) - non-redox. (a) N goes from +3 in $\mathrm{N}{\mathrm{O}}_2^{-}$ to +5 in $\mathrm{N}{\mathrm{O}}_3^{-}$ - redox. Hence (b), (c), (d).