In order to determine the identity of a particular lanthanide metal (M) ,a voltaic cell is constructed at 25°C with the anode consisting of the lanthanide metal as the electrode immersed in a solution of 0.0467 M MCl₃,and the cathode consisting of a copper electrode immersed in a 1.00 M Cu(NO₃) ₂ solution.The two half-reactions are as follows:
M(s) M³⁺(aq) + 3e^- Cu²⁺(aq) + 2e^- Cu(s)
The potential measured across the cell is 2.70 V.What is the identity of the metal?
Reduction Half-Reaction
E° (V)
Cu²⁺(aq) + 2e^- Cu(s) 0.34
Ce³⁺(aq) + 3e^- Ce(s) -2.336
Tm³⁺(aq) + 3e^- Tm(s) -2.319
Eu³⁺(aq) + 3e^- Eu(s) -1.991
Gd³⁺(aq) + 3e^- Gd(s) -2.279
Sm³⁺(aq) + 3e^- Sm(s) -2.304

Question

In order to determine the identity of a particular lanthanide metal (M) ,a voltaic cell is constructed at 25°C with the anode consisting of the lanthanide metal as the electrode immersed in a solution of 0.0467 M MCl₃,and the cathode consisting of a copper electrode immersed in a 1.00 M Cu(NO₃) ₂ solution.The two half-reactions are as follows:
M(s)

M³⁺(aq) + 3e^- Cu²⁺(aq) + 2e^-

Cu(s)
The potential measured across the cell is 2.70 V.What is the identity of the metal?
Reduction Half-Reaction
E° (V)
Cu²⁺(aq) + 2e^-

Cu(s) 0.34
Ce³⁺(aq) + 3e^-

Ce(s) -2.336
Tm³⁺(aq) + 3e^-

Tm(s) -2.319
Eu³⁺(aq) + 3e^-

Eu(s) -1.991
Gd³⁺(aq) + 3e^-

Gd(s) -2.279
Sm³⁺(aq) + 3e^-

Sm(s) -2.304

Quizplus · Accepted Answer

In order for the cell to produce a positive voltage, the reduction half-reaction at the cathode must have a higher standard reduction potential (E°) than the reduction half-reaction at the anode. Among the given options, Ce has the lowest E° of -2.336 V, indicating that it would be the anode in the cell. The reduction half-reaction for copper has the highest E° of 0.34 V, making it the cathode. Therefore, the metal at the anode must have a higher E° than copper but lower E° than Ce. Among the options, only Tm, Gd, Eu, and Sm have higher E° values than copper, but all of them have E° values lower than Ce. Therefore, the metal at the anode must be Ce.

In Order to Determine the Identity of a Particular Lanthanide