A voltaic cell is constructed in which a copper wire is placed in a 1.0 M CU(NO3

Question

A voltaic cell is constructed in which a copper wire is placed in a 1.0 M CU(NO3)2 solution and a strip of gold is placed in a 1.0 M AuNO3 solution. The measured potential of the cell is found to be 1.36V and the copper electrode is negative. The Edegree for the Cu^2+/Cu half-cell is +0.34 V. a. Since the copper electrode is negative, oxidation takes place at the copper electrode. Write the oxidation half-reaction for the Cu2/Cu half-cell and indicate its standard oxidation potential. Edegreeox. b. Write the half-reaction for the Au+/Au half-cell, c. Write the overall balanced oxidation-reduction and indicate the standard cell Potential Edegreecell. d. Calculate the standard reduction potential, Edegree red, for the Au+/Au half-cell.

Explanation / Answer

a) Since oxidation takes place at the copper electrode

Cu -> Cu2+ + 2e-

Eoox = - 0.34 V

b) Au+ + e- -> Au

c) Overall Reaction

Cu -> Cu2+ + 2e-

2Au+ + 2e- -> 2Au

Adding the two reactions

2Au+ + Cu ----> 2Au + Cu2+

Standard cell potential = E oxidation + E reduction = 1.36 V

Since the concentration of Cu(NO3)2 and AuNO3 are the same, the measured and the standard cell potential are the same

d) E reduction

1.36 = E oxidation + E reduction

=> 1.36 = -0.34 + E reducrion

=> E reduction = 1.7 V

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