Multiple Choice
In the following redox reaction: Cr2O7^{2-} + 3 HNO2 + 5 H^+ → 2 Cr^{3+} + 3 NO3^- + 4 H2O, which substance acts as the reducing agent?
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6. Chemical Quantities & Aqueous Reactions
Redox Reactions
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In the redox reaction 2 KMnO4 + 3 Na2SO3 + H2O → 2 MnO2 + 3 Na2SO4 + 2 KOH, which element is reduced?
A
Oxygen (O)
B
Manganese (Mn)
C
Potassium (K)
D
Sulfur (S)
Verified step by step guidance1
Identify the oxidation states of the elements involved in the reaction before and after the reaction to determine which element is reduced.
Focus on the element manganese (Mn) in potassium permanganate (KMnO4). In KMnO4, Mn typically has an oxidation state of +7.
Look at the product manganese dioxide (MnO2). In MnO2, manganese has an oxidation state of +4.
Since the oxidation state of manganese decreases from +7 to +4, manganese gains electrons and is therefore reduced.
Confirm that other elements either do not change their oxidation states or are oxidized, reinforcing that manganese is the element reduced in this reaction.
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