Electrochemistry Formulas

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The tendency of an electrode to lose electrons is called oxidation potential, while the tendency to gain electrons is called reduction potential.

EMF of a due cell is a measure of the free energy change which determines the tendency of the overall reaction to occur.

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If the EMF comes out to be positive, the reaction takes place.

Nernst Equation

Dependence of electrode potential and EMF on concentration and temperature.

For electrode potential;

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Gibbs Free Energy Change

Gibbs free energy change in an electrochemical reaction can be expressed as the equivalent of the potential difference.

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Concentration Cell

Concentration cells can be defined as the electrochemical cells in which the emf arises from a transfer of material from one electrode to another due to a concentration difference between the two.

In general for concentration cells.

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Electrolysis

The process of decomposition of an electrolyte by the passage of electricity through its aqueous solution or mole in the state is termed as Electrolysis. Electrodes that are utilized in the electrolysis of different electrolytes are of two types, 

  • Inert electrodes

  •  Active electrodes 

Faraday First Law of Electrolysis

Faraday’s first law of Electrolysis says that the mass of primary products formed at an electrode by electrolysis is directly proportional to the quantity of electricity passed.

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Faraday Second Law of Electrolysis

Faraday’s second law of electrolysis says that the masses of different primary products formed by equal amounts of electricity are proportional to the ratio of molar mass to the number of electrons involved with a particular reaction.

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Conductance

In relation to electrolytes, the term conductance (C) is used more frequently than resistance. Conductance implies the case with which electric current can flow through a conductor. It is defined as the reciprocal of resistance.

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Specific Conductance

Specific conductance = Conductance x Cell constant

Molar Conductance

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Equivalent Conductance

Equivalent conductance = (Molar conductance) / n

Where n = (Molecular mass)/(Equivalent mass)

Kohlrausch Law

The molar conductivity of an electrolyte at infinite dilution can be expressed as the sum of the ionic conductivities of cations and anions each multiplied by the number of ions present in one formula unit of the electrolyte.

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Applications of Kohlrausch Law

1. In the calculation of molar conductivity at infinite dilution for the weak electrolytes.

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2. In the calculation of the degree of dissociation.

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3. In the calculation of solubility of a sparingly soluble salt. As the solution is saturated but infinitely dilute.

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Where ‘u’ are ionic mobilities at infinite dilution?

Electrochemistry is the study of chemical processes that lead to electrons moving. When the movement of electrons takes place, then that is called electricity, which can be generated in a reaction known as an oxidation-reduction reaction by electrons from one element to another.

FAQ (Frequently Asked Questions)

Q1. Define Concentration Cell.

Ans - Concentration cells can be defined as the electrochemical cells in which the emf arises from a transfer of material from one electrode to another due to a concentration difference between the two.

Q2. What is Faraday’s Second Law of Electrolysis?

Ans - Faraday’s second law of electrolysis says that the masses of different primary products formed by equal amounts of electricity are proportional to the ratio of molar mass to the number of electrons involved with a particular reaction.