Question

In acidic solution, permanganate ion is reduced by ferrous ion. The number of electrons involved in the reduction of permanganate ion is ............

Hint:

Always determine oxidation state change to find electrons in redox reactions.

Answer 1

Correct Answer: 5

Step 1: Write oxidation state change.
Mn in \(\text{MnO}_4^{-}\): +7 Mn in \(\text{Mn}^{2+}\): +2 Step 2: Calculate change in oxidation state.
\[ 7 \rightarrow 2\quad \Rightarrow\quad \Delta = 5\ \text{electrons} \] Step 3: Balanced half-reaction (acidic medium).
\[ \text{MnO}_4^{-} + 8H^{+} + 5e^{-} \rightarrow \text{Mn}^{2+} + 4H_2O \] Step 4: Conclusion.
Number of electrons gained = 5.