Electrode potentials and cellsAQA A-Level Chemistry: Mind map

Exam questions on Electrode potentials and cells

1. A cell is set up with a zinc half-cell and a copper half-cell joined by a salt bridge. Standard electrode potentials: Zn²⁺(aq) + 2e⁻ ⇌ Zn(s), E° = −0.76 V; Cu²⁺(aq) + 2e⁻ ⇌ Cu(s), E° = +0.34 V.
   Write the equation for the overall cell reaction and state the direction of electron flow in the external circuit.2 marks
2. A student measures the standard electrode potential of the Ag⁺(aq) | Ag(s) half-cell by connecting it to a standard hydrogen electrode using a salt bridge and a voltmeter.
   Explain why a high-resistance voltmeter is used and what the purpose of the salt bridge is.2 marks
3. A chemist investigates the reactions of aqueous iron(II) and iron(III) ions with halogens and halide ions at standard conditions. Standard electrode potentials: Fe³⁺(aq) + e⁻ ⇌ Fe²⁺(aq), E° = +0.77 V; I₂(aq) + 2e⁻ ⇌ 2I⁻(aq), E° = +0.54 V; Br₂(aq) + 2e⁻ ⇌ 2Br⁻(aq), E° = +1.07 V.
   Use the electrode potentials to deduce whether iron(III) ions will oxidise iodide ions. Calculate the EMF and write an equation for any reaction.3 marks