8: Electrochemistry
- Page ID
- 453695
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- 8.1: Electrolytes Solutions are Nonideal at Low Concentrations
- A solution with a strong electrolyte produces multiple charged solutes in solution. We need to consider the dissociation process and stoichiometry of the salt, as well as the electrostatic interactions between the solutes. The result is that electrolytes behave nonideally even at low concentrations.
- 8.2: The Debye-Hückel Theory
- Debye and Hückel came up with a theoretical expression that makes is possible to predict mean ionic activity coefficients as sufficiently dilute concentrations. The theory considers the vicinity of each ion as an atmosphere-like cloud of charges of opposite sign that cancels out the charge of the central ion.
- 8.3: Extending Debye-Hückel Theory to Higher Concentrations
- The Debye–Hückel theory deviates from real systems at high concentrations because the model is simple and does not take into account effects such as ion association, incomplete dissociation, ion shape and size, polarizability of the ions, the role of the solvent. Several approaches have been proposed to extend the validity of the Debye–Hückel theory, including the Extended Debye-Hückel equation, the Davies equation, the Pitzer equations and specific ion interaction theory.
- 8.4: Electricity
- In 1799, Alessandro Volta showed that electricity could be generated by stacking copper and zinc disks submerged in sulfuric acid. The reactions that Volta produced in his voltaic pile included both oxidation and reduction processes that could be considered as half-reactions. The half-reactions can be classified as oxidation (the loss of electrons) which happens at the anode and reduction (the gain of electrons) which occurs at the cathode.
- 8.5: The connection to ΔG
- A criterion for spontaneity, \(\Delta G\) also indicated the maximum amount of non p-V work a system could produce at constant temperature and pressure. And since we is non p-V work, it seems like a natural fit to extend this discussion to electrochemistry.
- 8.6: Half Cells and Standard Reduction Potentials
- Much like G itself, E can only be measured as a difference, so a convention is used to set a zero to the scale. Toward this end, convention sets the reduction potential of the standard hydrogen electrode (SHE) to 0.00 V.
- 8.7: Entropy of Electrochemical Cells
- The Gibbs function is related to entropy through its temperature dependence and a similar relationship can be derived for the temperature variance of E.