A-Level Chemistry: Redox and Electrode Potentials

Redox chemistry runs from Year 1 oxidation states to Year 2 electrochemical cells, and this quiz covers the full arc.

The foundations are tested through the chlorine-in-alkali disproportionation (one element simultaneously oxidised to +1 and reduced to −1), oxidation state assignment in the dichromate ion (the 2x − 14 = −2 algebra giving +6), and the balanced half-equation for manganate(VII) reduction in acid — the 8H⁺, 5e⁻ workhorse of titration chemistry.

The electrochemistry questions build the full Year 2 apparatus. The standard hydrogen electrode is specified exactly: platinum electrode, hydrogen at 100 kPa, 1.0 mol dm⁻³ H⁺, defined as zero. Cell EMF is calculated twice — the iron/tin cell at +0.62 V and the aluminium/zinc cell at +0.90 V, the second requiring care with two negative electrode potentials. Feasibility prediction from the electrochemical series is tested through which metal/ion pairings give a positive cell EMF, and the series' logic — more positive means better oxidising agent — gets a dedicated question.

Practical electrochemistry completes the set: the alkaline hydrogen fuel cell with oxidation at the anode and reduction at the cathode, and the factors that shift a measured electrode potential away from its standard value (temperature and concentration — the Nernst territory A-level touches qualitatively).

Explanations always show the electron bookkeeping, which is the habit that makes redox reliable rather than memorised.

• Assign oxidation states and identify disproportionation
• Write and combine half-equations in acidic solution
• Specify the standard hydrogen electrode exactly
• Calculate cell EMF from standard electrode potentials, including double-negative cases
• Predict reaction feasibility from the electrochemical series and describe fuel cells

Aligned to the redox core of the DfE A level science subject content: oxidation states, half-equations, standard electrode potentials, cell EMF, feasibility and fuel cells.