Final answer:
Manganese (Mn) is the element that is reduced in the reaction 2 KMnO4 + 3 Na2SO3 + H2O → 2 MnO2 + 3 Na2SO4 + 2 KOH, as its oxidation state decreases from +7 to +4.
Step-by-step explanation:
In the given reaction 2 KMnO4 + 3 Na2SO3 + H2O → 2 MnO2 + 3 Na2SO4 + 2 KOH, we are asked to identify which element is reduced. To determine which element is reduced, we need to look at the changes in oxidation states for the elements involved in the reaction.
For manganese (Mn), in the reactant KMnO4, Mn has an oxidation state of +7, while in the product MnO2, Mn has an oxidation state of +4. A decrease in oxidation state indicates a reduction. Therefore, manganese is the element that is reduced in this reaction.
None of the other elements listed (sodium (Na), potassium (K), oxygen (O)) undergo a decrease in their oxidation states during this reaction, hence they are not reduced.