Nernst plots and formal potentials in a nonpolar solvent consisting of Al2Br6 and KBr in ethylbenzene

M. Elam, I. Bahatt, E. Peled, E. Gileadi

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Abstract

Nernst plots and formal potentials were determined for four metals (Pb, Sn, Cu, Ag). The two divalent ions (Sn, Pb) yield the expected slope of 2.3RT/2F. A maximum is observed when the concentration of the salt approaches that of free Al2Br6. This is accounted for quantitatively in terms of the various ionic species, i.e. [M(Al2Br7)]+, [M(Al2Br7)3]- and [M(AlBr4)]+, [M(AlBr4)3]- for a divalent metal (M), which can be stable in this nonpolar solvent system. Copper is found to occur in solution only in the monovalent state, even when CuBr2 is dissolved. The Nernst slope is (5/6)(2.3RT/F) which is consistent with the participation of both the positive ([Cu2(Al2Br7)]+ or [Cu2(AlBr4)]+) and negative ([Cu(Al2Br7)2]- or [Cu(AlBr4)2]-) complex ions in setting the equilibrium at the interface. For silver a Nernst slope of 23RT/F is observed Oxidation of lead or tin to the tetravalent state was not observed in the range of potential available up to bromine evolution When CuBr2 was dissolved, a disproportionation reaction took place, with formation of free bromine and monovalent copper as evidenced by the appearance of the bromo derivative of the solvent. A listing of formal potentials, measured here and in earlier publications shows that the scale of emf values is considerably compressed compared to that of aqueous solutions (from 2.75 V to 1.5 V).

Original languageEnglish
Pages (from-to)1609-1615
Number of pages7
JournalJournal of Physical Chemistry
Volume88
Issue number8
DOIs
StatePublished - 1984

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