Multiple Choice
Which of the following equations represents a redox reaction (a reaction in which oxidation numbers change)?
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6. Chemical Quantities & Aqueous Reactions
Redox Reactions
Multiple Choice
Which of the following is an example of reduction (as defined by a decrease in oxidation number)?
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Verified step by step guidance1
Step 1: Understand that reduction is defined as a decrease in oxidation number (oxidation state) of an element during a chemical reaction.
Step 2: Examine each given reaction and determine the oxidation number of the element of interest before and after the reaction.
Step 3: For the first reaction, Fe^{2+} \(\rightarrow\) Fe^{3+} + e^{-}, note that iron goes from +2 to +3, which is an increase in oxidation number, so this is oxidation, not reduction.
Step 4: For the second reaction, Cu^{2+} + 2e^{-} \(\rightarrow\) Cu, copper goes from +2 to 0, which is a decrease in oxidation number, indicating reduction.
Step 5: For the other reactions, similarly check the oxidation states: Cl^{-} \(\rightarrow\) \(\frac{1}{2}\)Cl_2 + e^{-} shows Cl going from -1 to 0 (oxidation), and Na \(\rightarrow\) Na^{+} + e^{-} shows Na going from 0 to +1 (oxidation). Therefore, the second reaction is the example of reduction.
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