The Student Room Group
Reply 2
Electrode potentials are relative to a H electrode, just like how we calculate moles relative to Carbon 12.
Anyhow, it measures a potential DIFFERENCE not an actual value.
Therefore you can' find a diff between an electrode and itself.....
Reply 3
It's about feasability. If you want to see if a reaction will happen you can chose your own two half-cells and measure the p.d. across them. This will be faster than setting up each reactant with a hydrogen half cell.

However, if you want to see is 30 reactions will happen: have three reactants A. B and C and react them each with 10 others, it is much easier to find their relative electrode potentials (setting the hydrogen cell to zero), which would be 13 experiments, than measuring the electrode potential for each experiment, which would be 30 experiments.

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