Standard electrode potentialsEdexcel A-Level Chemistry: Mind map

Exam questions on Standard electrode potentials

1. A teacher demonstrates three redox changes. In the first, sodium burns in chlorine: 2Na + Cl₂ → 2NaCl. In the second, orange acidified potassium dichromate(VI) turns green as it is reduced. In the third, purple acidified potassium manganate(VII) is decolourised when it is added to iron(II) sulfate solution.
   Use oxidation numbers and electron transfer to identify the species oxidised and the species reduced when sodium burns in chlorine.2 marks
2. To compare the tendency of different species to gain electrons, chemists measure electrode potentials against a single reference. The reference used is the standard hydrogen electrode, which is given an electrode potential of exactly 0.00 V.
   Explain why a reference electrode is needed to measure the standard electrode potential of a half-cell.2 marks
3. In Core Practical 10, a student investigates electrochemical cells by measuring standard electrode potentials. Each half-cell is connected to a standard hydrogen electrode so that a voltmeter can give the electrode potential. The student has zinc metal, zinc sulfate solution, iron(II) sulfate and iron(III) sulfate solutions, a platinum electrode, filter paper and potassium nitrate solution.
   Describe how the student sets up the zinc half-cell and connects it to the standard hydrogen electrode so that the standard electrode potential of Zn²⁺/Zn can be measured.3 marks