Multiple Choice
In the electrochemical cell based on the reaction Zn(s) + Cu^{2+}(aq) → Zn^{2+}(aq) + Cu(s), which of the following correctly lists the half-reactions occurring at the anode and cathode?
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6. Chemical Quantities & Aqueous Reactions
Redox Reactions
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Which element is being reduced in the following reaction?
Cr2O72- + 3 HNO2 + 5 H+ → 2 Cr3+ + 3NO3- + 4 H2O
A
Cr
B
H
C
N
D
O
Verified step by step guidance1
Identify the oxidation states of each element in the reactants and products. For example, in \( \text{Cr}_2\text{O}_7^{2-} \), chromium (Cr) has an oxidation state of +6, and in \( \text{Cr}^{3+} \), it is +3.
Determine the change in oxidation states for each element. A decrease in oxidation state indicates reduction, while an increase indicates oxidation.
For chromium (Cr), the oxidation state changes from +6 in \( \text{Cr}_2\text{O}_7^{2-} \) to +3 in \( \text{Cr}^{3+} \), indicating a reduction.
Check the oxidation states of other elements: nitrogen (N) in \( \text{HNO}_2 \) changes from +3 to +5 in \( \text{NO}_3^- \), indicating oxidation.
Conclude that the element being reduced is chromium (Cr), as its oxidation state decreases from +6 to +3.
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