Which is the oxidation half-reaction for Mn in Mn(s) → Mn2+(aq) + 2e-?

• A. Mn(s) → Mn2+ + 2e-
• B. Mn2+ + 2e- → Mn(s)
• C. Ti2+ + 2e- → Ti(s)
• D. None

Answer: (A)

Oxidation is the loss of electrons. In Mn(s) the manganese is in the 0 oxidation state, while Mn2+(aq) is +2. To go from 0 to +2, manganese must lose two electrons. That loss of electrons is shown on the product side of the half-reaction, giving Mn(s) → Mn2+ + 2e−. That’s why this is the oxidation half-reaction for manganese in this process. The reverse reaction Mn2+ + 2e− → Mn(s) would be a reduction. The option with Ti involves a different element, not manganese. And “None” isn’t correct because there is a valid oxidation half-reaction here.