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The terms anode and cathode are not defined by the voltage polarity of electrodes, but are usually defined by the direction of current through the electrode. An anode usually is the electrode of a device through which conventional current (positive charge) flows into the device from an external circuit, while a cathode usually is the electrode through which conventional current flows out of ...
Direct electrolysis of seawater follows known processes, forming an electrolysis cell in which the seawater acts as the electrolyte to allow for the reaction at the anode, 2 Cl − (aq) → Cl 2 (g) + 2e − and the reaction at the cathode, 2 H 2 O(l) + 2 e − → H 2 (g) + 2OH − (aq).
The cathode supplies electrons to the positively charged cations which flow to it from the electrolyte (even if the cell is galvanic, i.e., when the cathode is positive and therefore would be expected to repel the positively charged cations; this is due to electrode potential relative to the electrolyte solution being different for the anode ...
Electrolytic cells are often used to decompose chemical compounds, in a process called electrolysis—with electro meaning electricity [5] and the Greek word lysis means to break up. Important examples of electrolysis are the decomposition of water into hydrogen and oxygen , and bauxite into aluminum and other chemicals.
The net cell reaction yields hydrogen and oxygen gases. The reactions for one mole of water are shown below, with oxidation of oxide ions occurring at the anode and reduction of water occurring at the cathode. Anode: 2 O 2− → O 2 + 4 e −. Cathode: H 2 O + 2 e − → H 2 + O 2−. Net Reaction: 2 H 2 O → 2 H 2 + O 2
Electrolysis in pure water consumes/reduces H + cations at the cathode and consumes/oxidizes hydroxide (OH −) anions at the anode. This can be verified by adding a pH indicator to the water: Water near the cathode is basic while water near the anode is acidic.
Electrolysis is usually done in bulk using hundreds of sheets of metal connected to an electric power source. In the production of copper, these pure sheets of copper are used as starter material for the cathodes, and are then lowered into a solution such as copper sulfate with the large anodes that are cast from impure (97% pure) copper.
The Downs cell uses a carbon anode and an iron cathode.The electrolyte is sodium chloride that has been heated to the liquid state. Although solid sodium chloride is a poor conductor of electricity, when molten the sodium and chloride ions are mobilized, which become charge carriers and allow conduction of electric current.