Question

The $E_{{{M}^{3+}}/M{{n}^{2+}}}^{o}$ values for $Cr, Mn, Fe$ and $Co$ are $-0.41,+1.57,+0.77$ and $+1.97\,V$ respectively. For which one of these metals the change in oxidation state from $+ 2$ to $+ 3$ is easiest?

• A. $Cr$
• B. $Mn$
• C. $Fe$
• D. $Co$

Answer 1

Answer: (A)

$Cr$

Answer 2

More the negative value of standard reduction potential, higher is the reducing power and higher is the tendency to get oxidised. The $E{}^\circ$ value is most negative for $Cr$ among the given, hence it has higher tendency to change from $+2$ to $+3$ state.