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Electrochemical cell An electrochemical cell is a device that produces an electric current from energy released by a spontaneous redox reaction, this can be caused from electricity. This kind of cell includes the Galvanic cell or Voltaic cell, named after Luigi Galvani and Alessandro Voltaboth scientists who conducted several experiments on chemical reactions and electric current during the late 18th century.
Electrochemical cells have two conductive electrodes the anode and the cathode. The anode is defined as the electrode where oxidation occurs and the cathode is the electrode where the reduction takes place.
Electrodes can be made from any sufficiently conductive materials, such as metals, semiconductors, graphite, and even conductive and electric polymers.
In between these electrodes is the electrolytewhich contains ions that can freely move. The galvanic cell uses two different metal electrodes, each in an electrolyte where the positively charged ions are the oxidized form of the electrode metal.
One electrode will undergo oxidation the anode and the other will undergo reduction the cathode. The metal of the anode will oxidize, going from an oxidation state of 0 in the solid form to a positive oxidation state and become an ion.
At the cathode, the metal ion in solution will accept one or more electrons from the cathode and the ion's oxidation state is reduced to 0. This forms a solid metal that electrodeposits on the cathode.
The two electrodes must be electrically connected to each other, allowing for a flow of electrons that leave the metal of the anode and flow through this connection to the ions at the surface of the cathode.
This flow of electrons is an electric current that can be used to do work, such as turn a motor or power a light. A galvanic cell whose electrodes are zinc and copper submerged in zinc sulfate and copper sulfaterespectively, is known as a Daniell cell.
A shot glass -shaped container is aerated with a noble gas and sealed with the Teflon block. In this example, the anode is the zinc metal which is oxidized loses electrons to form zinc ions in solution, and copper ions accept electrons from the copper metal electrode and the ions deposit at the copper cathode as an electrodeposit.
This cell forms a simple battery as it will spontaneously generate a flow of electric current from the anode to the cathode through the external connection. This reaction can be driven in reverse by applying a voltage, resulting in the deposition of zinc metal at the anode and formation of copper ions at the cathode.
The simplest ionic conduction path is to provide a liquid junction. To avoid mixing between the two electrolytes, the liquid junction can be provided through a porous plug that allows ion flow while reducing electrolyte mixing.
To further minimize mixing of the electrolytes, a salt bridge can be used which consists of an electrolyte saturated gel in an inverted U-tube. As the negatively charged electrons flow in one direction around this circuit, the positively charged metal ions flow in the opposite direction in the electrolyte.
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A voltmeter is capable of measuring the change of electrical potential between the anode and the cathode. Electrochemical cell voltage is also referred to as electromotive force or emf. A cell diagram can be used to trace the path of the electrons in the electrochemical cell.
For example, here is a cell diagram of a Daniell cell: This is separated from its oxidized form by a vertical line, which represents the limit between the phases oxidation changes.
The double vertical lines represent the saline bridge on the cell. Finally, the oxidized form of the metal to be reduced at the cathode, is written, separated from its reduced form by the vertical line.Heroes and Villains - A little light reading.
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