What is the change in oxidation state of manganese?
A. +2
B. -2
C. +5
D. -5
D
Since oxygen has an oxidation state of -2, the manganese in the reactant must have an oxidation state of +7. As a product, the manganese has an oxidation state of +2. The oxidation state has decreased by 5, giving a change in oxidation state of -5.