1)

 Given below  are the half  -cell reactions

Mn2++eMn;E0=1.18eV

2(Mn3++eMn2+);E0=+1.51eV the E° for    3Mn2+Mn+2Mn3+ will be


A) -2.69 V; the reaction will not occur

B) -2.69; the reaction will occur

C) -0.33 V the reaction will not occur

D) -0.33 V the reaction will occur

Answer:

Option A

Explanation:

 Standard electrode potential  of reaction  [E°]  can be calculated as

   E0cell=EREP

where,  ER   = SRP of reactant

           EP   = SRP of product

   If      E0cell   = +ve  , then reaction is  spontaneous  otherwise non-spontaneous

Mn3+      E01=1.51V        Mn2+                

  Mn2+       E02=1.181V     Mn

   For   Mn2+ disproportionation

             E° =-1.51 V  - 1.18 v   =-2.69 v <  0