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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.
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.
Basic membrane cell used in the electrolysis of brine. At the anode (A), chloride (Cl −) is oxidized to chlorine. The ion-selective membrane (B) allows the counterion Na+ to freely flow across, but prevents anions such as hydroxide (OH −) and chloride from diffusing across. At the cathode (C), water is reduced to hydroxide and hydrogen gas ...
) ions flow to the anode to release electrons and a hydrogen (H +) ion to produce oxygen gas in an oxidation reaction. In molten sodium chloride (NaCl), when a current is passed through the salt the anode oxidizes chloride ions (Cl −) to chlorine gas, it releases electrons to the anode. Likewise, the cathode reduces sodium ions (Na +
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
Electrolyte can be fed on both anode and cathode side or anode side only. [10] In the zero-gap design of AWE, the electrodes are separated only by a diaphragm which separates the gases. The diaphragm only allows water and hydroxide ions to pass through, but does not completely eliminate gas cross-over.
The auxiliary electrode functions as a cathode whenever the working electrode is operating as an anode and vice versa. The auxiliary electrode often has a surface area much larger than that of the working electrode to ensure that the half-reaction occurring at the auxiliary electrode can occur fast enough so as not to limit the process at the ...
The exact relationship depends on the nature of the reactions at the two electrodes. For the electrolysis of aqueous copper(II) sulfate (CuSO 4) as an example, with Cu 2+ (aq) and SO 2− 4 (aq) ions, the cathode reaction is the reduction Cu 2+ (aq) + 2 e − → Cu(s) and the anode reaction is the corresponding oxidation of Cu to Cu 2+.