The standard reduction potential for the half-reaction: Sn4+ + 2e- --> Sn2+ is +
ID: 1020882 • Letter: T
Question
The standard reduction potential for the half-reaction: Sn4+ + 2e- --> Sn2+ is +0.15 V. Consider data from the table of standard reduction potentials for common half-reactions, in your text. For a galvanic cell under standard conditions, which of the following anodic half reactions would produce, at the cathode a spontaneous reduction of Sn4+ to Sn2+ but not Sn2+ to Sn.
yes no H2 + 2OH- --> 2H2O + 2e-
yes no Fe --> Fe3+ + 3e-
yes no Fe --> Fe2+ + 2e-
yes no Sn2+ --> Sn4+ + 2e-
yes no 2H2O --> 2H+ + H2O2 + 2e-
yes no Pb --> Pb2+ + 2e-
Explanation / Answer
Sn4+ + 2e- --> Sn2+ E0= +0.15 V.
Sn2+ + 2e- --> Sn. E0 = -0.13 V
in order to reduce sn^4+ to Sn^2+ , and not Sn2+ to Sn. the other electrode must have reduction potential lessthan 0.15 V and greater than -0.13 V
sothat
answer: Pb --> Pb2+ + 2e- , ( E0Pb^2+/Pb = -0.126 V)
Fe --> Fe3+ + 3e- ( E0Fe^3+/Fe = -0.04 V)
no H2 + 2OH- --> 2H2O + 2e-
yes Fe --> Fe3+ + 3e-
no Fe --> Fe2+ + 2e-
no Sn2+ --> Sn4+ + 2e-
no 2H2O --> 2H+ + H2O2 + 2e-
yes Pb --> Pb2+ + 2e-
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