electrochemical equivalent

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.{{Cite journal |last1=Richards |first1=Theodore William |last2=Collins |first2=Edward |last3=Heimrod |first3=George W. |date=1899 |title=The Electrochemical Equivalents of Copper and Silver |url=https://www.jstor.org/stable/25129912 |journal=Proceedings of the American Academy of Arts and Sciences |language=en |volume=35 |issue=8 |pages=123 |doi=10.2307/25129912|jstor=25129912 }}

This is an useful experimental quantity as it helps in many calculations in electrochemistry.{{Cite book |last=McKenzie |first=A. E. E. |title=General Physics |publisher=Cambridge University Press |year=1965 |isbn=9780471079217 |edition=3rd |location=London |page=336 |language=English |chapter=Magnetism and Electricity}}

The formula for finding electrochemical equivalent is as follows:

:$Z\; =\; M/q$

where $M$ is the mass of substance and $q$ is the charge passed. Since $q=It$, where $I$ is the current applied and $t$ is time, we also have

:$Z=M/It$

Alternative formula for finding electrochemical equivalent is as follows:

:$Z=E/F$

where $E$ is the Equivalent weight of the substance and $F$ is Faraday constant.{{Cite journal |last1=Richards |first1=Theodore William |last2=Collins |first2=Edward |last3=Heimrod |first3=George W. |date=1899 |title=The Electrochemical Equivalents of Copper and Silver |url=https://www.jstor.org/stable/25129912 |journal=Proceedings of the American Academy of Arts and Sciences |language=en |volume=35 |issue=8 |pages=123 |doi=10.2307/25129912|jstor=25129912 }}

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.

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Category:Physical chemistry

Category:Units of chemical measurement

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