Electrolytic reduction is a broader term referring to any reduction process that uses electrolysis, while electrolytic refining is a specific type of electrolysis used to purify metals.
Here's a breakdown of the key differences:
Electrolytic Reduction (General)
- Definition: A process that uses electrical energy to drive a non-spontaneous redox reaction, resulting in the reduction of a substance at the cathode. This encompasses a wide range of applications.
- Purpose: To obtain a specific element or compound from its ionic form. This can include producing pure metals from their ores, or creating other chemical substances.
- Electrode Material: The electrode material depends on the specific reaction. Inert electrodes like graphite or platinum are often used to prevent them from participating in the reaction. They can be of the same size.
- Electrolyte: Contains ions of the substance being reduced.
Electrolytic Refining (Specific)
- Definition: A specialized electrolytic process used to purify metals.
- Purpose: To obtain a high purity metal from an impure metal sample.
- Anode: Made of the impure metal that needs to be purified. During electrolysis, the impure metal dissolves into the electrolyte.
- Cathode: Made of a thin sheet of the pure metal. Metal ions from the electrolyte are deposited on the cathode, increasing its purity and size.
- Electrolyte: Contains a solution of a soluble salt of the metal being refined.
- Impurities: Impurities in the impure metal either dissolve in the electrolyte or collect as "anode mud" at the bottom of the electrolytic cell.
Table Summarizing the Differences
| Feature | Electrolytic Reduction | Electrolytic Refining |
|---|---|---|
| Purpose | To reduce a substance to its elemental form. | To purify a metal. |
| Anode | Can be inert or active, depends on the reaction. | Impure metal. |
| Cathode | Can be inert or active, depends on the reaction. | Pure metal (thin sheet). |
| Electrolyte | Contains ions of the substance being reduced. | Contains a soluble salt of the metal being refined. |
| Overall Process | A general term for electrolysis used for reduction. | A specific type of electrolysis used specifically for refining. |
Example
- Electrolytic Reduction: Producing aluminum from alumina ($Al_2O_3$) using the Hall-Héroult process.
- Electrolytic Refining: Purifying copper from blister copper.
In short, electrolytic refining is a specific application of electrolytic reduction that focuses on metal purification. Electrolytic reduction is a broader term encompassing any reduction process driven by electrolysis.
