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


Tm


Gd


Ce


Eu


Sm