Learn how to set up a galvanic cell and determine the EMF

This helpful video from the University of Birmingham links electrochemistry to metals more broadly and identifies displacement reactions as a useful precursor to electrochemical cells.

The Daniell cell is a particular type of galvanic cell using copper and zinc cathodes in beakers of copper sulfate and zinc sulfate respectively. The following two videos from amritacreate and SpaceyScience show the same experiment using slightly different apparatus. Comparing and contrasting the different set-ups can be a helpful way to probe students’ understanding of the underlying chemistry and why one set-up might be preferable to another.

Questions you can ask your students:

  • What is the purpose of the salt bridge?
  • What can be used instead of an inverted U-tube for the salt bridge?
  • Why are the experimenters using solutions with concentrations of 1 mol dm-3?
  • What would the voltmeter reading be if you switched the connections, connecting the copper rod to the negative terminal and the zinc rod to the positive terminal?
  • Write down the half equation taking place at each cathode and write the overall redox equation for the cell.

It’s helpful for students to determine the EMF for various electrochemical cells and then compare their results with the calculated Ecell using tables of standard electrode potentials. Why might their experimental results be different?

 E°cell = E°cathode - E°anode

It’s also worth being aware of microscale approaches to electrochemical cells, with one possible technique being demonstrated in the video below from the NCSSM. This microscale approach allows you to easily, quickly and inexpensively compare multiple ‘cells’ using a variety of metal pieces as cathodes.

Also check out…

  • Nailing corrosion demonstrations – Declan Fleming presents an experiment to illustrate the electrochemistry of rusting using phenolphthalein and hexacyanoferrate(III) as indicators.
  • Explaining electrolytes explicitly – the latest research indicates that students’ grasp of electrolyte chemistry may not be as well developed as we assume.
  • How to teach displacement reactions – this CPD article offers advice on how to help students develop an understanding of the reactivity of metals; a useful precursor to electrochemistry.
  • Battery power – the perfect resource for when you need an overview of the many different types of batteries and their histories.