Question

Among the four successive members of the first series of the transition metals listed below in the options, which one has a positive standard potential $\left(E_{M^{2+}/M}^0\right)$ value?

• A. $Ni(Z=28)$
• B. $Cu(Z=29)$
• C. $Fe(Z=26)$
• D. $Co(Z=27)$

Answer 1

Answer: (B)

$Cu(Z=29)$

$E^0{M}^{2+}|M{Ni}^{2+}|Ni=-0.23,{Cu}^{2+}|Cu=0.34F{e}^{2+}|Fe=-0.44,{Co}^{2+}|Co=-0.28$

$E^0{Cu}^{2+}|Cu$ is $+ve$

Standard reduction potential of ${Cu}^{2+}⟶Cu$ is positive because after reduction $Cu$ is formed. And $Cu$ has fully filled stable $\left(d^{10}\right)$ configuration.