Question

$C{r}_2{O}_7^{{}_2}+H_{2}O+3S{O}_2\to 2C{r}^{+3}+2O{H}^{-}+3S{O}_4^{-2}$

write down to oxidation and reduction reaction

Answer 1

${}^{+6}C{r}_2^{-2}{O}_7^2{+}^1{H}_2{O}^{-2}{+}^{4}S{O}_2^{-2}{⟶}^{+3}C{r}^{3+}{+}^{-2}O\stackrel{1}{H^{-}}{+}^{+6}S\stackrel{-2}{O_4^{2-}}$

Oxidation: ${}^{4}S{O}_2^{-2}{⟶}^{6}S\stackrel{-2}{O_4^{2-}}+2e^{-}$

Reduction: $6e^{-}+C{r}_2^6\stackrel{-2}{O_7^{2-}}⟶2\stackrel{+3}{C{r}^{3+}}$

$O:S{O}_2+2H_{2}O⟶S{O}_4^{2-}+2e^{-}+4H^{+}$

$R:C{r}_2{O}_7^{2-}\stackrel{+6e^{-}+14H^{+}}{\to }2C{r}^{3+}+7H_{2}O$

$3S{O}_2+C{r}_2{O}_7^{2-}+6H_{2}O+6e^{-}+14H^{+}⟶3S{O}_4^{2-}+2C{r}^{3+}+6e^{-}+7H_{2}O+12H^{+}$

$3S{O}_2+C{r}_2{O}_7^{2-}+2H^{+}⟶3S{O}_4^{2-}+2C{r}^{3+}+H_{2}O$