A standard voltaic cell is constructed using Cu metal in 1.0 M Cu(NO3)2(aq) and an unknown metal in a 1.0 M solution of its nitrate salt. The cell voltage is 0.47 V when the Cu half-cell is the cathode. What is the standard
reduction potential of the unknown metal? [E°Cu = 0.34 V]
(A) –0.81 V
(B) –0.13 V
(C) 0.13 V
(D) 0.81 V
Let the `E^0_(red)` value for the other cell having the unknown metal in a 1.0 M solution of its nitrate salt be V volts. All the electrolytes are in standard (1.0 M) concentration.
`E^0(cell) = E^0(cath)-E^0(anod) = (0.34-V)` volts
By the condition of the problem:
`rArr V=0.34-0.47=-0.13` volts
Therefore, the standard reduction potential of the unknown metal is -0.13 volts (option B).