Question

$2 \text{MnO}_4^{-} + b \text{I}^{-} + c \text{H}_2\text{O} \rightarrow x \text{I}_2 + y \text{MnO}_2 + z \text{OH}^{-}$
If the above equation is balanced with integer coefficients, the value of $z$ is \\_\\_\\_\\_\\_\\_.

Answer 1

Reduction Half Reaction:

$2\text{MnO}_4^- \rightarrow 2\text{MnO}_2$ $2\text{MnO}_4^- + 4\text{H}_2\text{O} + 6e^- \rightarrow 2\text{MnO}_2 + 8\text{OH}^-$

Oxidation Half Reaction:

$2\text{I}^- \rightarrow \text{I}_2 + 2e^-$ $6\text{I}^- \rightarrow 3\text{I}_2 + 6e^-$

Adding the oxidation half and reduction half, we get the net reaction as:

$2\text{MnO}_4^- + 6\text{I}^- + 4\text{H}_2\text{O} \rightarrow 3\text{I}_2 + 2\text{MnO}_2 + 8\text{OH}^-$

Thus, $z = 8$.