Need help with quick HSC multiple choice question - oxidation numbers

[preliminary17hsc18]

Hi, just need some help with the question please

In which of the following equations is the metal reduced? (These are not balanced equations.)
(A) [Fe(CN)6]4– → [Fe(CN)6]3–
(B) [MnO4]– → MnO2.
(C) [MnO4]2– → [MnO4]–.
(D) [Cr2O7]2– → [CrO4]2–

[MisterNeo]

Hi, just need some help with the question please

In which of the following equations is the metal reduced? (These are not balanced equations.)
(A) [Fe(CN)6]4– → [Fe(CN)6]3–
(B) [MnO4]– → MnO2.
(C) [MnO4]2– → [MnO4]–.
(D) [Cr2O7]2– → [CrO4]2–

Hi
Oxidation is the loss of electrons (becomes more positive), whereas reduction is the gain of electrons (becomes more negative). A metal being reduced occurs when a metal cation gains electrons and its charge decreases because it becomes less positive.

B: Mn in the reactant side has an oxidation state of +7 (7 + 4(-2) = -1), and on the product side, Mn has an oxidation state of +4 (4 + 2(-2) = 0). The state has decreased which means Mn has gained electrons to become more negative, hence the metal has being reduced.

Option A: Fe went from +2 to +3.
Option C: Mn went from +6 to +7.
Option D: Cr went from stays as +6 on both sides.