Electrolysis Concepts |
Key Concepts
- Electrolysis: the process in which an electric current is used to bring about a chemical reaction which does not occur spontaneously (Eo for the electrolytic cell is negative*).
- Electrolytic Cell: converts electrical energy into chemical energy.
Applied emf must be greater than the emf for the cell, ie greater than Eo for the spontaneous redox reaction.
- Electrodes : conductors used to permit the flow of electrons in an electrochemical cell.
One electrode is the anode, the other is the cathode.
- Anode: Oxidation occurs at the anode.
Anions (negatively charged ions) migrate to the anode.
Anode is positive.
Anode disintegrates.
- Cathode: Reduction occurs at the cathode.
Cations (positively charged ions) migrate to the cathode.
Cathode is negative.
Solid deposits at the cathode.
- Electron flow: from anode to cathode.
Electrons flow from positive to negative.
- If more than one reaction is possible, the reaction with the lowest Eo will occur.
- Mass of substance produced electrolytically is proportional to the quantity of electricity flowing.
Examples of Electrolysis and Electrolytic Cells
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| *This discussion assumes that all species are present in their standard states so that the electrode potentials are standard electrode potentials. |
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