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

Abstract

An important intermediate goal to evaluate our concept for the assumption-free determination of single-ion Gibbst ransfer energies D tr G8 8(i, S 1 !S 2 )i sp resented. We executed the crucial steps a) and b) of the methodology, described in Part Iofthis treatise,exemplarily for Ag + and Clwith 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 as alt bridge cancel, if the bridge electrolyte is an "ideal" ionic liquid, that is,o ne 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.

Density Functional Theory Descriptors for Ionic Liquids and the Introduction of a Coulomb Correction

“…80 Unfortunately, we could not reproduce the values given in the publication, but obtained a Δq NE value of 0.10 e. This suggests that the values for Δq NE in Table 7 should be treated with caution. Using the diffusion data from recent and carefully conducted measurements, 87 Δq NE even takes a value 81 This poses a problem for the use of Δq NE since the theoretical charge transfer values do not contain any temperature dependence. It is unclear how to compare experimental values for different systems measured at different temperatures.…”

Evaluation and validation of detailed and simplified models of the uncertainty of unified pHabsH2O measurements in aqueous solutions

“…The cell has two compartments connected by a capillary tube filled with an ionic liquid, [N2225][NTf2] in this case, thus establishing a salt bridge between the two solutions, 1 and 2. Although the measured potential difference incorporates liquid junction potentials at both junctions, the use of this ionic liquid is assumed to cancel out the residual liquid junction potential contribution [17,18], [19]. This is the reason why no correction is made to the measured potential.…”

Single-ion activity: a nonthermodynamically measurable quantity

“…Although this was among the best we have tried [10,15,28,32], and was recently confirmed by Lindner et al [20], there must be many better alternatives in view of the tuned mobilities of the IL-constituent cation and anion, the solubility in water, the environmentally friendliness, etc. For bridging an aqueous solution and an organic phase, Krossing's group proposed a new IL consisting of cation and anion having nearly equal mobilities and successfully used it to minimize the liquid junction potential across the aqueous-organic boundary [6,26].…”