Question

sodium bromide and potassium permanganate undergo a redox reaction in basic solution according to the skeleton equation given. which half-reaction skeleton represents the reduction?
br⁻ + mno₄⁻ → bro₃⁻ + mno₂
a. br⁻ → bro₃⁻
b. mno₄⁻ → mno₂
enter the answer choice letter.

Explanation:

To determine the reduction half - reaction, we look at the change in oxidation states. In a reduction reaction, the oxidation state of an element decreases. For Mn in \(MnO_4^-\), the oxidation state of Mn is +7 (let \(x\) be the oxidation state of Mn, \(x + 4\times(-2)=- 1\), so \(x = + 7\)). In \(MnO_2\), the oxidation state of Mn is +4 ( \(x+2\times(-2) = 0\), so \(x = + 4\)). The oxidation state of Mn decreases from +7 to +4, so \(MnO_4^-\to MnO_2\) is the reduction half - reaction. In option A, the oxidation state of Br in \(Br^-\) is - 1 and in \(BrO_3^-\) is +5, so the oxidation state increases, meaning it is an oxidation half - reaction.

Answer:

B