| 词条 | Half-cell |
| 释义 |
A half-cell is a structure that contains a conductive electrode and a surrounding conductive electrolyte separated by a naturally occurring Helmholtz double layer. Chemical reactions within this layer momentarily pump electric charges between the electrode and the electrolyte, resulting in a potential difference between the electrode and the electrolyte. The typical anode reaction involves a metal atom in the electrode dissolved and transported as a positive ion across the double layer, causing the electrolyte to acquire a net positive charge while the electrode acquires a net negative charge. The growing potential difference creates an intense electric field within the double layer, and the potential rises in value until the field halts the net charge-pumping reactions. This self-limiting action occurs almost instantly in an isolated half-cell; in applications two dissimilar half-cells are appropriately connected to constitute a Galvanic cell. A standard half-cell, used in electrochemistry, consists of a metal electrode in a 1 molar (1 mol/L) aqueous solution of the metal's salt, at 298 kelvins (25 °C).[1] The electrochemical series, which consists of standard electrode potentials and is closely related to the reactivity series, was generated by measuring the difference in potential between the metal half-cell in a circuit with a standard hydrogen half-cell, connected by a salt bridge. The standard hydrogen half-cell: 2H+(aq) + 2e− → H2(g) The half-cells of a Daniell cell: Original equation Zn + Cu2+ → Zn2+ + Cu Half-cell (anode) of Zn Zn → Zn2+ + 2e− Half-cell (cathode) of Cu Cu2+ + 2e− → Cu See alsoStandard electrode potential (data page)References1. ^{{cite book |last=Andrews |first=Donald H. |author2=Richard J. Kokes |title=Fundamental Chemistry |publisher=John Wiley & Sons, Inc. |location=New York |year=1962 |page=482 |chapter=Electrochemistry}} {{Electrolysis}}{{Galvanic cells}} 2 : Electrochemistry|Electrochemical cells |
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