Multiple Choice
Which of the following represents the balanced equation for the overall redox reaction between Fe³⁺(aq) and Cr(s) based on their standard reduction potentials?
20. Electrochemistry
Standard Reduction Potentials
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Using standard reduction potentials, calculate the standard emf for the following reaction: Co(s) + 2Co³⁺(aq) → 3Co²⁺(aq). What is the standard emf of this reaction?
A
0.77 V
B
0.51 V
C
0.28 V
D
1.23 V
Verified step by step guidance1
Identify the half-reactions involved in the overall reaction. The given reaction involves the oxidation of Co(s) to Co²⁺(aq) and the reduction of Co³⁺(aq) to Co²⁺(aq).
Write the oxidation half-reaction: Co(s) → Co²⁺(aq) + 2e⁻. Determine the standard reduction potential for this half-reaction, which is the reverse of the reduction potential for Co²⁺(aq) to Co(s).
Write the reduction half-reaction: Co³⁺(aq) + e⁻ → Co²⁺(aq). Look up the standard reduction potential for this half-reaction in a standard reduction potential table.
Calculate the standard emf (E°) of the overall reaction using the formula: E° = E°(reduction) - E°(oxidation). Substitute the standard reduction potentials obtained from the table into this formula.
Ensure the stoichiometry of the electrons is balanced in the overall reaction. If necessary, multiply the half-reactions by appropriate coefficients to balance the electrons before calculating the standard emf.
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