Half Cell Reactions
Electrochemical cells rely on the same basic principle as the reactions happening on individual electrodes (half-cell reactions). These reactions involve the electrode losing or gaining electrons (oxidation or reduction). The standard potential of an electrode tells us its natural tendency to gain or lose electrons compared to a reference point. This potential helps predict the direction of the overall reaction in the cell. These cells use the combined process of oxidation and reduction (redox) to generate electricity. The voltage produced is likely linked to the movement of electrons during these reactions within the cell. The half cell reaction for a Zn-Cu cell is given as follows:
Oxidation Half Cell Reaction
This occurs at anode. In this half-cell reaction, solid zinc (Zn) undergoes oxidation to form zinc ions (Zn2+(aq)) and release two electrons(2e–). The standard electrode potential associated with this half-reaction can be measured against the standard hydrogen electrode (SHE).
Zn(s) → Zn2+(aq) + 2e–
Reduction Half-Cell Reaction
This occurs at cathode. Here, copper ions (Cu 2+(aq)) gain two electrons (2e −) to form solid copper (Cu(s)) through reduction. The standard electrode potential of this half-reaction can also be determined relative to the SHE.
Cu2+(aq) + 2e → Cu(s)
By comparing the standard electrode potentials of various half-cell reactions, we can predict the overall spontaneity of a redox reaction. In a galvanic cell, the half-cell with the more positive standard electrode potential undergoes reduction, while the half-cell with the less positive standard electrode potential undergoes oxidation. This difference in electrode potentials drives the flow of electrons through the external circuit, generating electrical energy.
Standard Electrode Potential
Standard electrode potential (E°) is a measure of the tendency of a half-reaction to occur as a reduction at a standard condition. In the context of standard electrode potential, “standard conditions” refer to a set of specific conditions under which the potential is measured. It includes standard concentration of all aqueous species to be 1 mol/L, pressure to be 1 atm and temperature to be 25℃ or 298K.
In this article, we will learn in detail about standard electrode potential, its formula, construction, factors affecting and applications.
Table of Content
- What is Standard Electrode Potential?
- Standard Electrode Potential Formula
- Construction of Standard Electrode Potential
- Difference Between Electrode Potential and Standard Electrode Potential
- Factors Affecting Electrode Potentials
- Standard Electrode Potential Example
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