Table of Contents
Electrochemical Series: Application, Characteristics of the Electrochemical Series
Introduction:
Electrochemistry is described as the discipline of physical chemistry that studies the link between electricity, as a measured and quantitative phenomenon, and detectable chemical change. In this case, electricity is seen as a result of a certain chemical change, or vice versa. Electric charges travelling between electrolyte and electrode are examples of these processes. As a result, electrochemistry is concerned with the interplay between chemical and electrical energy.
An electrochemical cell is a device that generates an electric current by harnessing the energy produced by a spontaneous redox reaction that may be induced by electricity. Voltaic cells and galvanic cells, named after Luigi Galvanic and Alessandro volts, are examples of this sort of cell. During the late 18th century, both scientists did a number of studies on chemical reactions and electric current.
In electrochemical cells, there are two conducting electrodes: cathode and anode. The anode is the electrode where oxidation takes place. The cathode, on the other hand, is the electrode where the reduction occurs. Any suitably conducting substance, such as graphite, semiconductors, metals, or even conductive polymers, can be used to create electrodes. The electrolyte sits between these electrodes, which contain ions that can freely migrate.
Electrochemical Series
An electrochemical series, also known as an activity series, is a list that defines the arrangement of components in ascending order of increasing electrode potential values. The series was created by comparing the potential of several electrodes to that of a conventional hydrogen electrode (SHE).
The electrodes (metals and nonmetals) in contact with their ions are organized in an electrochemical series based on the values of their standard reduction or oxidation potentials. The voltage measured when the half cell is connected to the standard hydrogen electrode under standard circumstances yields the standard electrode potential.
Electropositive and Electronegative Elements
Electropositive elements (other than hydrogen) are those that have a stronger tendency to lose electrons to their solution. Elements that gain electrons are also known to be electronegative. They are commonly found below the element hydrogen in the periodic table. In any event, we may deduce the sequence in which metals will replace one another from their salts by looking at the electrochemical series. As a result, electropositive metals often replace hydrogen from acids.
Application of Electrochemical Series:
1. Oxidizing and Reducing Strengths
The electrochemical series can help us find a good oxidizing or reducing agent. All of the substances at the top of the electrochemical series are good oxidizing agents, i.e., they have a positive value of standard reduction potential, whereas those at the bottom are good reducing agents, i.e., they have a negative value of standard reduction potential. For example, the F2 electrode with a standard reduction potential of +2.87 volts is a powerful oxidizing agent, whereas Li+ electrode with a standard reduction potential of -3.05 volts is a strong reducing agent.
2. Electrochemical Cell Standard Emf (E0) Calculation
The cell’s standard emf is the sum of the standard reduction potentials of the two halves: half-cell reduction and half-cell oxidation
Eocell = Eored + Eoox
The standard oxidation potential is always represented in terms of reduction potential by convention.
As a result, the standard oxidation potential (Eoox) = − the standard reduction potential (Eored).
Therefore,
Eocell = (reduction half cell standard reduction potential) – (standard reduction potential of oxidation half cell)
Because oxidation occurs at the anode and reduction occurs at the cathode. Hence,
Eocell = Eocathode – Eoanode
3. Predicting Redox Reaction Possibility
If the free energy change (ΔG) is negative, any redox reaction will occur spontaneously. The free energy is linked to the cell emf in the following way:
ΔGo = nFEo
Where n represents the number of electrons involved, F represents the Faraday constant, and Eo represents the cell emf.
If Eo is positive, ΔGo might be negative.
When Eo is positive, the cell response is spontaneous and acts as an electrical energy source.
If the result is negative, the spontaneous response cannot occur.
The calculated Eo value for redox reaction is useful in forecasting the stability of a metal salt solution when kept in another metal container.
4. Predicting the Electrolysis Product
In the presence of two or more types of positive and negative ions in solution, certain metal ions are discharged or freed at the electrodes in preference to others during electrolysis. In such a competition, the ion with the higher oxidizing potential (high value of standard reduction potential) is discharged first at the cathode.
Thus, when an aqueous solution of NaCl containing Na+, Cl–, H+, and OH– ions is electrolyzed, H+ ions are preferentially deposited at the cathode (reduction) rather than Na+ ions, since the reduction potential of hydrogen (0.00 volt) is greater than the reduction potential of sodium (0.00 volt) (-2.71 volt). The anion with the lowest reduction potential will be oxidized at the anode where oxidation occurs. As a result, OH– with a standard reduction potential of 0.40 volt will be oxidized over Cl– with a standard reduction potential of 1.36 volt.
Important Characteristics of the Electrochemical Series
- The electrochemical series takes an element’s reduction potential in relation to the hydrogen scale, where Eo = 0. The definition of an element’s standard reduction potential is “the measure of an element’s likelihood to undergo reduction.”
- The larger an element’s reduction potential, the easier it is to decrease. Elements with a low reduction potential, on the other hand, will be oxidized considerably more quickly and readily.
- Elements having a negative or lower reduction potential, on the other hand, readily give up electrons. Elements with a positive) or greater reduction potential do not readily give away electrons but readily receive electrons.
- Stronger reducing agents with a negative standard reduction potential are often found in the electrochemical series below hydrogen. In the series, however, weaker reducing agents with positive standard reduction potential are identified above the hydrogen.
- As we travel down the group, the strength of the reducing agent increases while the strength of the oxidizing agent drops.
- Similarly, as we progress through the series, the electro-positive and activity of metals increases or intensifies. It reduces in the case of nonmetals.
FAQ’s
What is the configuration of the Electromagnetic Series?
The electrochemical series is constructed by arranging several redox equilibria in the order of their standard electrode potentials, also known as redox potentials. The most negative Eo values are placed at the top of the electrochemical series, while the most positive values are placed at the bottom.
Define a basic EMF Series.
The elements might be listed according to the conventional electrode potential. A hydrogen gas electrode is used as a standard reference and is set to zero. All of the potentials are either positive or negative in relation to the hydrogen electrodes, commonly known as the EMF series.
List the two parts of the Electrochemical Series.
The electrochemical series is made up of two half cells, each of which has an electrode and an electrolyte. The two half cells may utilize the same electrolyte or may use separate electrolytes at times.
