electrochemistry - Reduction Potential in electrochemical cell

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 a series of three posts. The first one is:

(a) To Determine Ecell of an electrochemical cell.

An electrochemical cell consists of an anode and a cathode, each in their respective half-cell. The cells are linked together by a salt bridge. Using Cu²⁺ + e <-> Cu, generally a Cu half-cell will contain Cu and Cu²⁺.

When this half-cell is connected to another half-cell (e.g the H₂ half-cell), a potential difference is caused because of the different ease of reduction of the two species.

Since, the reduction potential of Cu²⁺ is more positive than the H⁺ (+0.34V against 0V), electrons flows from the H₂ half-cell (which is less willing to be reduced thus oxidation occurs) to the Cu²⁺ half-cell (where reduction is more favoured). Thus, cell voltage will be +0.34 - 0 = +0.34V.

From this, it results in the equation Ecell = Ereduction half-cell - Eoxidation half-cell. when Ecell > 0, the reduction potential of the reduction half-cell must be greater than the oxidation half-cell. And in simple terms, where one particular cell prefers reduction more than the other cell.

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Article written by Kwok YL 2007.

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