Electrochemistry - Reduction Potentials in electrolysis

In an earlier entry on the topic of Electrochemistry -Reduction Potential, I spoke about my interpretation of reduction potential, whose main tenet is for us to decide which substance is more susceptible to reduction and which is less. Therefore, having the positive and negative sign is IMPORTANT.

In this entry I would be writing about the application (or uses) of the Standard Reduction Potential. There are three main uses, (a) to determine the Ecell of an electrochemical cell. (b) to determine whether a redox reaction will occur and (c) deciding which substance will be electrolysed. These will be discussed in three series of posts. The third and final one is:

(c) Using reduction potential for electrolysis.

In (a), we actually converted chemical energy into electrical energy. While in electrolysis, the converse actually occurs. We are supplying electrical energy such that a chemical reaction occurs.

Hence, we are looking out for reduction process whose reduction potential is less positive, therefore requiring energy aid for reaction to occur.

While in the case of oxidation processes, we are looking for their corresponding reduction potential to be more positive. This would me that the reduction step is favourable and the oxidation is not, hence, energy will have to be supplied such that the oxidation step can occur.

In addition, most of the times the electrolytes given are quite clear to whether it would be made to oxidised or reduce. Only water is ambiguous as it can be made to oxidised or reduced.

When there are two species which can be reduced (or oxidised), we will compare the reduction potential (or corresponding reduction potential) and the one with lower energy requirement will be reduced (or oxidised).

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Article written by Kwok YL 2007.

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