The Ideal Ionic Liquid Salt Bridge for Direct Determination of Gibbs Energies of Transfer of Single Ions, Part II: Evaluation of the Role of Ion Solvation and Ion Mobilities.

An important intermediate goal to evaluate our concept for the assumption-free determination of single-ion Gibbs transfer energies Δ _tr G°(i, S ₁ →S ₂ ) is presented. We executed the crucial steps a) and b) of the methodology, described in Part I of this treatise, exemplarily for Ag ⁺ and Cl ^- with S ₁ being water and S ₂ being acetonitrile. The experiments showed that virtually all parts of the liquid junction potentials (LJPs) at both ends of a salt bridge cancel, if the bridge electrolyte is an "ideal" ionic liquid, that is, one with nearly identical diffusion of anion and cation. This ideality holds for [N ₂₂₂₅ ] ⁺ [NTf ₂ ] ^- in the pure IL, but also in water and acetonitrile solution. Electromotive force measurements of solvation cells between S ₁ and S ₂ demonstrated Nernstian behavior for Ag ⁺ concentration cells and constant like cell potentials for solutions with five tested Ag ⁺ counterions.
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