Q.
The EM3+/M2+o values for Cr, Mn, Fe and Co are -0.41, +1.57, +0.77 and +1.97 V respectively. For which one of following metal the change in oxidation state from +2 to +3 easiest?
Here ERPo of Cr = - 0.41 so its EOPo is 0.41.
As here EOPo for Cr2+/Cr3+ is maximum +0.41 V so Cr2+ will be easily oxidised to Cr3+ .
For rest of the metals EOPo will be negative so they have less tendency to be oxidized then Cr here.