Q12 / 200 · Manipal (MET) 2010 · Chemistry

$E^{\circ}$ values of $\mathrm{Mg}^{2+} / \mathrm{Mg}$ is -2.37 V , of $\mathrm{Zn}^{2+} / \mathrm{Zn}$ is -0.76 V and $\mathrm{Fe}^{2+} / \mathrm{Fe}$ is -0.44 V . Which of the statements is correct?

  • Correct answer
    A
    Zn will reduce $\mathrm{Fe}^{2+}$
  • B
    Zn will reduce $\mathrm{Mg}^{2+}$
  • C
    Mg oxidises Fe
  • D
    Zn oxidises Fe

Solution

Higher the negative value of $E^{\circ}$, more is the reducing power. The order of $E^{\circ}$ values (negative value) is $-\frac{2.37}{(\mathrm{Mg})}\gt-\frac{0.76}{(\mathrm{Zn})}\gt-\frac{0.44}{(\mathrm{Fe})}$ $\therefore \mathrm{Mg}$ can reduce both $\mathrm{Zn}^{2+}$ and $\mathrm{Fe}^{2+} . \mathrm{Zn}$ can reduce $\mathrm{Fe}^{2+}$, but not $\mathrm{Mg}^{2+}$. Fe cannot reduce Mg and Zn but can oxidise them.

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

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