Equivalent number

The equivalent number is the number of electrons exchanged in an electrochemical reaction . It is often referred to as or z . With the help of the equivalent number, a relationship between the metabolic rate of the electrochemical reaction and the electrical current flow can be established. Since the flow of current can easily be determined by means of an electrical current measurement, electrochemical reactions can be determined quantitatively very easily. ${\displaystyle n_{e}}$

For example, the equivalent number of galvanic copper deposition from a copper sulfate solution is 2.

${\displaystyle \mathrm {\ {Cu}^{2+}+\ 2\ {e}^{-}\rightarrow \ {Cu}} }$

The connection arises from Faraday's law

${\displaystyle n={\frac {Q}{n_{e}F}}}$

With

• n amount of deposited substance ,
• F is the Faraday constant and
• Q is the amount of charge that has flowed .

With a current flow of 1 ampere, 5.2 · 10 ⁻⁶ mol per second are deposited. This corresponds to 1.2 g per hour.

Additive:

The equivalent number z does not refer to the substance, but to the behavior of the substance in a reaction and corresponds to the previously used term " valence ".

It is defined for the following reactions:

Neutralization : z = number of H ⁺ - od OH. ^- - ions, which exchanges the particle

Redox reaction : z = number of electrons exchanged, i.e. the change in the oxidation state

Ion reaction : z = amount of the charge number of the ion

See also

• Electrochemical equivalent
• Valence (chemistry)