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

Correct Answer: 8

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, \( z = 8 \).