There was this question I had to do on which went like "which all metals can we not extract using electrolysis from aq soln" the answer involved the effect of solvent on electrode potentials, can someone care to explain/ lead me to sources which will?


The short answer is that we want a cathodic reaction so we can use the metals with a positive standard reduction potential (because 0 is for $\ce{H2} $ reduction).

In reality however to really find a suitable electrolyte cyclic voltammetry is typically used and electrolytes with suitable electrochemical windows for the cell reaction are chosen.

enter image description here The electrochemical window is the voltages where the current is zero in the picture above. If the wrong electrolyte is chosen then a full redox reaction happens(with the electrolyte participating) rather than half reactions at each electrode negating the need for the external circuit and creating heat

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  • $\begingroup$ what is this? electrolyte cyclic voltammetry and if current is there that means transfer of ions hence redox right? $\endgroup$ – DDD4C4U Nov 9 '19 at 8:11
  • $\begingroup$ We know that*Nernst eqn $$ \Delta G=-nFE $$ so a spontaneous reaction occurs at negative gibbs free energy or positive cell potentials(E). The cell potential can be calculated using a standard reduction table Ecell=Eoxidation+ Ereduction. With water hydrogen ions are reduced at zero volts so if a metal with a +ve oxidation potential (aka a metal with a negative reduction potential) were in the presence of water it would be oxidized and hydrogen ion would be reduced (+ve Ecell). So with WATER we use positive reduction potentials but with other electrolytes it depends on its reduction potentials $\endgroup$ – ChemEng Feb 10 at 1:31

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