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A feasible cell was constructed by joining the two half cells below. Cu\(^{2+}\) (aq) +...

Chemistry
WAEC 2001

A feasible cell was constructed by joining the two half cells below. Cu\(^{2+}\) (aq) + 2e\(^-\) → Cu(s) E\(^0\) = +0.34 V; Zn\({^2+}\) + 2e\(^-\) → Zn\((_s)\) E\(^0\) = - 0.76V. What is the standard e.m.f. of the cell?

  • A. - 1.1V
  • B. - 0.42V
  • C. +0.42V
  • D. +1.1V
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Correct Answer: Option D
Explanation

The standard e.m.f. of a cell is calculated by subtracting the standard reduction potential of the anode from the standard reduction potential of the cathode:

                       E\(^0\)\(_{cell}\) =  E\(^0\)\(_{cathode}\) - E\(^0\)\(_{anode}\)

 Since   E\(^0\)\(_{Cu^{2+}}\)  >   E\(^0\)\(_{Zn^{2+}}\), it can be inferred that Copper is reduced at the cathode while Zinc is oxidized at the anode.

                       E\(^0\)\(_{cell}\) =  E\(^0\)\(_{Cu^{2+}}\)  -  E\(^0\)\(_{Zn^{2+}}\)

                                              = + 0.34 - (- 0.76)

                                              = + 0.34 + 0.76

                                              = +1.10V

The standard e.m.f. of the cell is +1.10V  

                                             

 


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