Write a balanced half-reaction for the oxidation of solid manganese dioxide to permanganate ion in basic aqueous solution. Be sure to add physical state symbols where appropriate.

8 OH⁻(aq) + Mn(s) ⇒ MnO₄⁻(aq) + 4 H₂O(l) + 7 e⁻

Explanation:

Let's consider the following oxidation half-reaction that takes place in basic aqueous solution.

Mn(s) ⇒ MnO₄⁻(aq)

First, we will perform the mass balance. We will add 4 H₂O to the products side and 8 OH⁻ to the reactants side.

8 OH⁻(aq) + Mn(s) ⇒ MnO₄⁻(aq) + 4 H₂O(l)

Finally, we will perform the charge balance by adding 7 electrons to the products side.

8 OH⁻(aq) + Mn(s) ⇒ MnO₄⁻(aq) + 4 H₂O(l) + 7 e⁻