Question

What amount of electric charge is required for the reduction of 1 mole of MnO$_4^{2-}$ into Mn$^{2+}$?

• A. 1F
• B. 5F
• C. 4F
• D. 6F

Hint:

For redox reactions, remember that the number of electrons involved is key to calculating the charge required.

Answer 1

The Correct Option is C

To reduce MnO$_4^{2-}$ to Mn$^{2+}$, we need to consider the change in oxidation state of Mn. In MnO$_4^{2-}$, Mn is in the +2 oxidation state, and in Mn$^{2+}$, Mn is also in the +2 state. Thus, no change in oxidation state occurs. However, the reduction process involves the addition of 2 electrons per ion, and for 1 mole of MnO$_4^{2-}$, 4 moles of electrons are required. 
This corresponds to a charge of 4 Faradays.