5.2.3
Redox and
Electrode
Potentials
Section 5.2.3 covers oxidising and reducing agents, constructing redox equations from half-equations and oxidation numbers, redox titrations with Fe²⁺/MnO₄⁻ and I₂/S₂O₃²⁻ and with unfamiliar redox systems, standard electrode (redox) potentials and the hydrogen electrode, measuring and calculating standard cell potentials, predicting feasibility and the limits of those predictions in terms of kinetics and concentration, modern storage cells and fuel cells.
Revision Notes
8 revision notes, in the order the specification teaches them.
Redox, Oxidation Numbers and Half-Equations
Redox: electron transfer, oxidation numbers, oxidising and reducing agents and constructing redox equations from half-equations.
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Standard Electrode Potentials and the Hydrogen Electrode
The standard electrode (redox) potential: half-cells, standard conditions of 298 K, 100 kPa and 1.00 mol dm⁻³, and the standard hydrogen electrode.
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Electrochemical Cells and Cell Potentials
Electrochemical cells: half-cells, the salt bridge, measuring cell potentials and calculating the standard cell potential.
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The Electrochemical Series and Feasibility of Reactions
The electrochemical series: oxidising and reducing agents, predicting feasibility from E⦵ values and the limitations of the predictions.
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Storage Cells
Storage cells: electrode reactions, overall equations and cell voltage from electrode potential data.
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Fuel Cells
Fuel cells: the hydrogen–oxygen fuel cell, electrode half-equations and the overall reaction.
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Redox Titrations: Iron(II) and Manganate(VII)
Redox titrations with potassium manganate(VII) and iron(II): equations, method, end point and calculations.
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Redox Titrations: Iodine and Thiosulfate
Iodine–thiosulfate titrations: equations, the starch indicator, method and calculations.
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Electrode Potentials Map
OCR A Level Chemistry A · 5.2.3A Electrode potentials and cells
The whole section on one A4 page: half-equations, standard electrode potentials, cells and E⦵cell, the electrochemical series and feasibility, the limits of predictions, and storage and fuel cells.
Redox Titrations Map
OCR A Level Chemistry A · 5.2.3B Redox titrations
The whole section on one A4 page: manganate(VII) with iron(II), the titration itself, other reducing agents, iodine and thiosulfate, ratios through iodine, and non-familiar systems.
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5.2.3
- d i
the techniques and procedures used when carrying out redox titrations including those involving Fe2+/MnO4– (see also 2.1.5 e–f)
Revise - d ii
the techniques and procedures used when carrying out redox titrations including those involving I2/S2O32– (see also 2.1.5 e–f)
Revise - e (i) a
structured and non-structured titration calculations, based on experimental results of redox titrations involving Fe2+/MnO4–
Revise - e (i) b
structured and non-structured titration calculations, based on experimental results of redox titrations involving I2/S2O32–
Revise - e (ii)
structured and non-structured titration calculations, based on experimental results of redox titrations involving non-familiar redox systems
Revise - g (i)
the techniques and procedures used for the measurement of cell potentials of metals or non-metals in contact with their ions in aqueous solution
Revise - g (ii)
the techniques and procedures used for the measurement of cell potentials of ions of the same element in different oxidation states in contact with a Pt electrode
Revise - i ii
the limitations of predictions of feasibility using standard cell potentials in terms of kinetics
Revise - i iii
the limitations of predictions of feasibility using standard cell potentials in terms of concentration
Revise - k i
explanation that a fuel cell uses the energy from the reaction of a fuel with oxygen to create a voltage
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