Redox Equilibria

Redox Equilibria

1. understand the terms ‘oxidation’ and ‘reduction’ in terms of electron transfer and changes in oxidation number, applied to s-, p- and d-block elements

   • In terms of electron transfer: 1. Oxidation is loss of electrons 2. Reduction is gain of electrons
   • In terms of changes in Oxidation number: 1. An element in a species is oxidised when its oxidation number increases. 2. An element in a species is reduced when its oxidation number decreases.

2. know what is meant by the term ‘standard electrode potential’, Eo

   • The standard electrode potential of a half cell is the emf measured when a half cell is connected to the standard hydrogen electrode. Standard conditions are 298K, 100 kPa pressure of gases and solution concentrations of 1 moldm-3 apply.

3. know that the standard electrode potential, Eo, is measured in conditions of: i 298 K temperature ii 100 kPa pressure of gases iii 1.00 mol dm-3 concentration of ions

4. know the features of the standard hydrogen electrode and understand why a reference electrode is necessary

5. understand that different methods are used to measure standard electrode potentials of: i metals or non-metals in contact with their ions in aqueous solution ii ions of the same element with different oxidation numbers

6. be able to calculate a standard emf, Eocell , by combining two standard electrode potentials

7. be able to write cell diagrams using the conventional representation of half-cells

8. understand the importance of the conditions when measuring an electrode potential, E

9. be able to use standard electrode potentials to predict the thermodynamic feasibility of a reaction

10. understand that Eo cell is directly proportional to the total entropy change and to lnK for a reaction

11. understand the limitations of predictions made using standard electrode potentials, in terms of kinetic stability of systems and departure from standard conditions

12. know that standard electrode potentials are sometimes referred to as standard reduction potentials and can be listed as an electrochemical series

13. understand how standard electrode potentials can be used to predict the thermodynamic feasibility of disproportionation reactions

14. be able to carry out both structured and unstructured titration calculations involving redox reactions, including iron(II) ions and potassium manganate(VII) and sodium thiosulfate and iodine

15. be able to discuss the uncertainty of measurements and their implications for the validity of the final results

16. understand that fuel cells use the energy released on the reaction of a fuel with oxygen to generate a voltage Knowledge that methanol and other hydrogen-rich fuels are used in fuel cells is expected.

17. know the electrode reactions that occur in a hydrogen-oxygen fuel cell Knowledge of hydrogen-oxygen fuel cells with both acidic and alkaline electrolyte is expected.