Standard electrode potentials and the hydrogen electrodeEdexcel International A Level Chemistry: Mind map

Exam questions on Standard electrode potentials and the hydrogen electrode

1. Acidified potassium dichromate(VI) is used to oxidise iron(II) ions to iron(III) ions in a laboratory analysis. The ionic equation for the reaction is: Cr₂O₇²⁻ + 14H⁺ + 6Fe²⁺ → 2Cr³⁺ + 6Fe³⁺ + 7H₂O
   Explain, in terms of electrons and oxidation number, why the dichromate(VI) ion acts as an oxidising agent in this reaction.2 marks
2. A student sets up a standard hydrogen electrode (SHE) to use as the reference when measuring electrode potentials.
   Explain why platinum is used as the electrode in the standard hydrogen electrode.2 marks
3. A student measures the standard electrode potential of the Fe³⁺(aq)|Fe²⁺(aq) half-cell and, separately, of the Zn²⁺(aq)|Zn(s) half-cell, in each case by connecting the half-cell to a standard hydrogen electrode.
   Describe how the student would set up the Fe³⁺(aq)|Fe²⁺(aq) half-cell and complete the circuit so that its standard electrode potential can be measured.3 marks