24.2.3—Measuring standard electrode potentials
- Syllabus
- 9701–2028–2029
- Objective
- 24.2.3
- Level
- A2
Measure standard electrode potentials by coupling a half-cell to the SHE or another reference
To measure E° for a metal/ion pair, connect the half-cell to the SHE through a salt bridge and high-resistance voltmeter. For two oxidation states of one element, use an inert platinum electrode in each solution.
Maintain standard concentrations, gas pressure and temperature, record polarity and write both reduction half-equations. The measured cell voltage gives the difference in reduction potentials.
Fe³⁺/Fe²⁺ uses Pt|Fe³⁺,Fe²⁺, while Zn²⁺/Zn uses Zn metal in Zn²⁺ solution. Each is paired with the SHE to obtain a reference value.
A salt bridge completes ion flow but does not supply electrons, and an inert Pt electrode is required when no solid conductor is present.
ConceptA-Level CAIE Chemistry A2