A voltaic cell consists of an Mn/Mn2+ half-cell and a Pb/Pb2+ half-cell. Calculate [Pb2+] when [Mn2+] is 1.5 M and Ecell is 0.17 V.
Pb2+ + 2e- --------------> Pb Eo = - 0.13 V
Mn2+ + 2e- ---------------> Mn Eo = - 1.18 V
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Mn + Pb2+ ----------------> Mn2+ + Pb
Eocell = -0.13 - (-1.18 ) = + 1.05 V
no of electrons transferred n = 2
Given that Ecell = + 0.17 V
[Mn2+] = 1.5 M
Ecell = Eocell - (0.059/n) Iog {[Mn2+]/[Pb2+]} where n = no of electrons transferred
+ 0.17 = + 1.05 - (0.059/2) Iog {[1.5 ]/[Pb2+]}
(0.059/2) Iog {[1.5 ]/[Pb2+]} = 0.88
[Pb2+] = 2.2 x 10-30 M
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