Determination Of E0 Research Articles

Activity Coefficients of NaBr in Aqueous Mixtures with High Relative Permittivity Cosolvent: Formamide + Water at 298.15 K

The mean ionic activity coefficients of NaBr were experimentally determined in formamide + water mixtures at 298.15 K from potential difference measurements of the following electrochemical cell containing two ion selective electrodes (ISEs): Na-ISE|NaBr (m), formamide (w), H2O (1–w)|Br-ISE. The molality (m) varied between 0.02 mol·kg–1 and almost saturation, whereas the mass fraction of formamide in the mixture (w) was varied between 0 and 1 in 0.1-unit steps. The determination of E0* (molal scale) was carried out following a method similar to that proposed by Hitchcock and using the classical extended Debye–Hückel and Scatchard equations. We also use for this purpose a modification of the Pitzer equation proposed by Rard and Archer and the most recent modified three-characteristic-parameter-correlation model. The results obtained produced good internal consistency, within the normal limits of experimental error in these types of measurement. Once E0* was determined, the mean ionic activity coefficients of NaBr (γ), the Gibbs energy of transfer of the NaBr from the water to the formamide + water mixture (ΔGt0), standard solubility product of NaBr in formamide + water (Ksp0), and NaBr primary hydration number (nhyd) were estimated. The results were comparatively analyzed with those of NaF and NaCl previously obtained in similar mixtures.

Activity Coefficients of NaClO4 in Aqueous Solution

The activity coefficients of NaClO4 in water were experimentally determined at (288.15, 298.15, and 308.15) K from electromotive force (emf) measurements of the following electrochemical cell without transference containing two ion-selective electrodes (ISEs): Na-ISE|NaClO4 (m)|ClO4-ISE. The molality m varied between about (0.02 and 12) mol·kg–1. The determination of E0*, which is necessary to calculate the activity coefficients, was carried out following a method similar to that of Hitchcock, using the Pitzer, extended Debye–Huckel, and Scatchard equations to represent the dependency of log γ on molality. The electrode system employed shows good Nernstian behavior. The activity and osmotic coefficients obtained in this study at 298.15 K were contrasted to those from the literature and show a good agreement.

Determination of E0 for the UO2+ 2 /U4+ Couple from Measurement of the Equilibrium: UO2+ 2 + Cu(s) + 4H+ = U4+ + Cu2+ + 2H2O at 25°C and some Geochemical Implications

Article Determination of E0 for the UO2+2 /U4+ Couple from Measurement of the Equilibrium: UO2+2 + Cu(s) + 4H+ = U4+ + Cu2+ + 2H2O at 25°C and some Geochemical Implications was published on May 1, 1991 in the journal Radiochimica Acta (volume 54, issue 3).

The charge—potential relationship in polyconjugated conducting polymers. Determination of E0 and N-values for polypyrrole and polythiophene

Experimental charge—voltage relationships for reversible oxidation of polypyrrole (PP) and polythiophene (PT) in acetonitrile were obtained. Curve-fitting analysis according to Feldberg's model for mixed faradaic and capacitive contributions provides the E 0 and n-values of these materials. PP shows a single process at E 0 = −0.66 V ( vs ag/Ag +) with n = 0.6, while PT shows two isoelectronic processes at E 0 = 0.28 and 0.58 V with n = 0.3. The single process for PP is due to merging of two one-electron processes involving polaron and bipolaron species. PT is suggested to be involved in 0.5-electron steps possibly due to dimeric associations in the polymer chain.

Polarization effects in pion-photoproduction on protons below 500 MeV. II

Using the same model as in the previous paper a prediction for the polarization of the recoil protons is given in case of polarized photons. The determination ofE 0+ andE 1+ from measurements is discussed. Furthermore the influence of theππ-interaction on polarization is considered. In the case ofπ +-production the polarization of the recoil neutrons is investigated and the dependence of the cross section on the polarization state of the target protons is discussed.