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In 1836 the British chemist John Frederic Daniell (1790-1845) proposed an improved electric cell that supplied an even current during continuous operation. Daniell cell consisted of a glass jar containing copper and zinc electrodes, each immersed in their respective acidic sulphate solutions. The two solutions were separated by a porous clay cylinder separator. It was a galvanic cell in which the spontaneous electrodissolution of zinc and electroplating of copper provided the electrical current.
Zn(s) |
→ | Zn2+ + 2e- |
+0.763 V |
Cu2+ + 2e- |
→ | Cu(s) |
+0.337 V |
Zn(s) + Cu2+ |
→← | Zn2+ + Cu(s) |
+1.100 V |
Nitrogen was discovered by Daniel Rutherford (Scotland) in 1772. The origin of the name comes from the Greek words nitron genes meaning nitre and forming and the Latin word nitrum (nitre is a common name for potassium nitrate, KNO3). It is colourless, odourless, generally inert gas. Minimally reactive at room temperature. A component of many organic and inorganic compounds. Makes up about 78 % of earth’s atmosphere. Nitrogen is obtained from liquid air by fractional distillation. Primarily to produce ammonia and other fertilizers. Also used in making nitric acid, which is used in explosives. Also used in welding and enhanced oil recovery.
Galvanic cell (voltaic cell) is a simple device with which chemical energy is converted into electrical energy. Galvanic cells consist of two separate compartments called half cells containing electrolyte solutions and electrodes that can be connected in a circuit. Two dissimilar metals (e.g., copper and zinc) are immersed in an electrolyte. If the metals are connected by an external circuit, one metal is reduced (i.e., gains electrons) while the other metal is oxidized (i.e., loses electrons).
In the example above, copper is reduced and zinc is oxidized. The difference in the oxidation potentials of the two metals provides the electric power of the cell.
A voltaic cell can be diagrammed using some simple symbols. In the diagram the electrodes are on the outer side of the diagram and a vertical line (|) is used to separate the electrode from the electrolyte solution found in the compartment. A double vertical line (||) is used to separate the cell compartments and is symbolic of the salt bridge. Usually in a diagram the species oxidized is written to the left of the double slash. Here is an example of the Daniell cell:
The names refer to the 18th-century Italian scientists Alessandro Volta (1745-1827) and Luigi Galvani (1737-1798).
Generalic, Eni. "Daniell." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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