Question
Given below are the half-cell reactions
Mn2+ + 2e- → Mn; Eo = - 1.18 eV
2(Mn3+ + e- →Mn2+); Eo = +1.51 eV
The Eo for 3Mn2+ → Mn + 2Mn3+ will be
-
-2.69 V; the reaction will not occur
-
-2.69 V; the reaction will occure
-
-0.33 V; the reaction will not occur
-
-0.33 V; the reaction will occur
Solution
A.
-2.69 V; the reaction will not occur
Standard element potential of reaction [ Eo] can be calculated as
Eocell = ER-EP
where ER = SRP of reactant
EP = SRP of product
If Eocell = +ve, then the reaction is spontaneous otherwise non-spontaneous.
therefore, For Mn2+ disproportionation
Eo = - 1.51 V - 1.18 V = - 2.69 V < 0
