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

### 1 Answer | Add Yours

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.

So,

`E^0(cell) = E^0(cath)-E^0(anod) = (0.34-V)` volts

By the condition of the problem:

`(0.34-V)=0.47`

`rArr V=0.34-0.47=-0.13` volts

Therefore, the standard reduction potential of the unknown metal is -0.13 volts (**option B**).

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