Summary
♦ Redox reaction: a chemical reaction in which electrons are gained or lost
♦ Primary cell and electrolytic cell: Primary cell is a device that converts chemical energy into electrical energy by redox reaction. Electrolytic cell is a device that converts electrical energy into chemical energy directly by electrolysis reaction.
♦ Standard Electrode Potential
- Definition of standard electrode potential: the standard potential difference of the oxidation/reduction pair (half-electrode) with respect to SHE in the standard state.
- What is the standard state: a pure substance (monomers or compounds) at a standard pressure (Po = 105 Pa) and at the temperature at which the experiment is carried out (usually 25°C).
- How to measure the standard electrode potential: By forming a Harned cell and changing the hydrochloric acid concentration CHCl by various means according to γA → 1 in the infinite dilution state, the electric potential E is measured each time, and when the electric potential is extrapolated to CHCl → 0, the E obtained is the standard electrode potential Eo.
- Electric potentials and thermodynamic quantities : Calculate Eo thermodynamically using the equations for the electric potential E = -ΔG/nF and ΔGo = ΔHo - TδSo.
- Standard electrode potential of Li+/Li:
- The free energy of dissolution was measured and the standard electrode potential for Li+/Li was calculated to be -3.045 V using thermodynamic methods.
- Indirect method measurements: The potentials of the Li metal and Li amalgam electrodes in dehydrated propylamine were first measured, and then the potentials of the Li amalgam electrode and the calomel electrode in aqueous solution were measured, yielding a standard potential of -3.3044 V for the calomel electrode for Li+/Li.
- The free energy of dissolution was measured and the standard electrode potential for Li+/Li was calculated to be -3.045 V using thermodynamic methods.
♦ Nernst equation: Two meanings of balance - equilibrium potential; balance of battery voltage.
♦ Eq. Potential: The Eq. Potential of a system whose potential varies with solution pH is constant at constant pH; the Eq. Potential of a system formed by a complex depends on the equilibrium constant of the coordination reaction and is constant.
Topic:
Part I: Review of Redox Reaction ยท Galvanic Cells and Electrolytic Cells
Part II: Definition of Standard Electrode Potential
Part III: Standard State and Standard Electrode Potential Measurement
Part IV: Electric Potential and Thermodynamic Quantities
Part V: Standard electrode potential of Li+/Li & Nernst equation
Part VI: Two meanings of equilibrium
Part VII: Formal potential