Chemistry:Electrochemical equivalent
In Electrochemistry, the electrochemical equivalent (Eq or Z) of a chemical element is the mass of that element (in grams) transported by a specific quantity of electricity, usually expressed in grams per coulomb of electric charge.[1] The electrochemical equivalent of an element is measured with a voltameter.
Definition
The electrochemical equivalent of a substance is the mass of the substance deposited to one of the electrodes when a current of 1 ampere is passed for 1 second, i.e. a quantity of electricity of one coulomb is passed.[2]
This is an useful experimental quantity as it helps in many calculations in electrochemistry.[3]
The formula for finding electrochemical equivalent is as follows:
where is the mass of substance and is the charge passed. Since , where is the current applied and is time, we also have
Alternative formula for finding electrochemical equivalent is as follows:
where is the Equivalent weight of the substance and is Faraday constant.[4]
Experimental analysis of electrochemical equivalent
For example to determine the ECE of copper, a copper voltameter is often used. In this device, a vessel which consist of copper sulfate solution and in which two electrodes of copper are dipped. The middle plate is cathode and other outer plates are used as anode, this allows a deposit of copper to accumulate into the faces of copper cathode plates. The voltameter is connected in series with the battery, an ammeter, rheostat and switch. The cathode is first dried and weighed precisely. The current is switched on and measured as soon as possible and with a limited value of charge density (usually 1 A for every 50 m2). This is because if charge density is too much, the deposit may not stick with cathode and will wash off.[3]
Eq values of some elements in kg/C
| Element | Electrochemical equivalent |
|---|---|
| Silver (Ag) | 1.118×10^(-6)
0.00118gm/c |
| Copper (Cu)[5] | 3.295×10^(-7) |
| Gold (Au) | 6.812×10^(-7) |
| Iron (Fe) | 2.894×10^(-7) |
| Zinc (Zn) | 3.389×10^(-7) |
| Hydrogen (H2) | 1.04472×10^(-8) |
| Sodium (Na) | 2.387×10^(-7) |
| Potassium (K) | 4.055×10^(-7) |
| Oxygen (O2) | 8.28×10^(-8) |
| Aluminum (Al) | 9.36×10^(-8) |
References
- ↑ "Definition of ELECTROCHEMICAL EQUIVALENT" (in en). https://www.merriam-webster.com/dictionary/electrochemical+equivalent.
- ↑ Richards, Theodore William; Collins, Edward; Heimrod, George W. (1899). "The Electrochemical Equivalents of Copper and Silver" (in en). Proceedings of the American Academy of Arts and Sciences 35 (8): 123. doi:10.2307/25129912. https://www.jstor.org/stable/25129912.
- ↑ 3.0 3.1 McKenzie, A. E. E. (1965). "Magnetism and Electricity" (in English). General Physics (3rd ed.). London: Cambridge University Press. p. 336. ISBN 9780471079217.
- ↑ Richards, Theodore William; Collins, Edward; Heimrod, George W. (1899). "The Electrochemical Equivalents of Copper and Silver" (in en). Proceedings of the American Academy of Arts and Sciences 35 (8): 123. doi:10.2307/25129912. https://www.jstor.org/stable/25129912.
- ↑ Richards, Theodore William, Edward Collins, and George W. Heimrod. “The Electrochemical Equivalents of Copper and Silver.” Proceedings of the American Academy of Arts and Sciences 35, no. 8 (1899): 123–50. https://doi.org/10.2307/25129912.
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