Q47 / 120 · NEET 2012 (Mains) · Chemistry

Four successive members of the first series of the transition metals are listed below. For which one of them the standard potential $\left(E_{M^{2+} / M}^{\circ}\right)$ value has a positive sign?

  • A
    $\operatorname{Co}(Z=27)$
  • B
    $\mathrm{Ni}(Z=28)$
  • Correct answer
    C
    $\mathrm{Cu}(Z=29)$
  • D
    $\mathrm{Fe}(Z=26)$

Solution

In electrochemical series metals with positive standard potential are placed below hydrogen. Out of the given transition metals, only $\mathrm{Cu}$ is placed below hydrogen in the electrochemical series. Therefore, it must have positive sign for standard potential.

Hence, the correct answer is option: 'C'.

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