Chemistry - Redox Reactions Question with Solution | TestHub

With ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7,{\mathrm{SO}}_2$ works as reducing agent. $\begin{array}{rl}{\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7+{\mathrm{H}}_2{\mathrm{SO}}_4+3{\mathrm{SO}}_2⟶& {\mathrm{K}}_2{\mathrm{SO}}_4+\\ & {\mathrm{Cr}}_2{\left({\mathrm{SO}}_4\right)}_3+{\mathrm{H}}_2\mathrm{O}\end{array}$ With water the reaction is not a redox reaction, $\begin{array}{rl}& {\mathrm{SO}}_2+{\mathrm{H}}_2\mathrm{O}⟶{\mathrm{H}}_2{\mathrm{SO}}_3\\ & 2\mathrm{Mg}+{\mathrm{SO}}_2⟶2\mathrm{MgO}+\mathrm{S}\\ & 3\mathrm{Mg}+{\mathrm{SO}}_2⟶2\mathrm{MgO}+\mathrm{MgS}\end{array}$