When an electric current passes through an electrolytic cell, how can we recognizer that electrolysis is taking place?
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when charge is moving from - to+ charge then electrons moves so we can easily identify that electrolysis takes place e
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Voltaic cells use a spontaneous chemical reaction to drive an electric current through an external circuit. These cells are important because they are the basis for the batteries that fuel modern society. But they aren't the only kind of electrochemical cell. It is also possible to construct a cell that does work on a chemical system by driving an electric current through the system. These cells are calledelectrolytic cells. Electrolysis is used to drive an oxidation-reduction reaction in a direction in which it does not occur spontaneously.
The Electrolysis of Molten NaCl
An idealized cell for the electrolysis of sodium chloride is shown in the figure below. A source of direct current is connected to a pair of inert electrodes immersed in molten sodium chloride. Because the salt has been heated until it melts, the Na+ ions flow toward the negative electrode and the Cl- ions flow toward the positive electrode.

When Na+ ions collide with the negative electrode, the battery carries a large enough potential to force these ions to pick up electrons to form sodium metal.
Negative electrode (cathode): Na+ + e-  Na
Cl- ions that collide with the positive electrode are oxidized to Cl2 gas, which bubbles off at this electrode.
Positive electrode (anode): 2 Cl-  Cl2 + 2 e-
The net effect of passing an electric current through the molten salt in this cell is to decompose sodium chloride into its elements, sodium metal and chlorine gas.
Electrolysis of NaCl: Cathode (-): Na+ + e-  Na Anode (+): 2 Cl-  Cl2 + 2 e-
The potential required to oxidize Cl- ions to Cl2 is -1.36 volts and the potential needed to reduce Na+ ions to sodium metal is -2.71 volts. The battery used to drive this reaction must therefore have a potential of at least 4.07 volts.
The Electrolysis of Molten NaCl
An idealized cell for the electrolysis of sodium chloride is shown in the figure below. A source of direct current is connected to a pair of inert electrodes immersed in molten sodium chloride. Because the salt has been heated until it melts, the Na+ ions flow toward the negative electrode and the Cl- ions flow toward the positive electrode.

When Na+ ions collide with the negative electrode, the battery carries a large enough potential to force these ions to pick up electrons to form sodium metal.
Negative electrode (cathode): Na+ + e-  Na
Cl- ions that collide with the positive electrode are oxidized to Cl2 gas, which bubbles off at this electrode.
Positive electrode (anode): 2 Cl-  Cl2 + 2 e-
The net effect of passing an electric current through the molten salt in this cell is to decompose sodium chloride into its elements, sodium metal and chlorine gas.
Electrolysis of NaCl: Cathode (-): Na+ + e-  Na Anode (+): 2 Cl-  Cl2 + 2 e-
The potential required to oxidize Cl- ions to Cl2 is -1.36 volts and the potential needed to reduce Na+ ions to sodium metal is -2.71 volts. The battery used to drive this reaction must therefore have a potential of at least 4.07 volts.
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