The electrochemical series is a sequence of half cells grouped in ascending electrode potential order. On the left are oxidants, and on the right are their conjugate reductants. The voltage produced when a half cell is linked to the hydrogen half-cell, indicated in red in the electrochemical series on the right, under typical conditions, is the electrode potential of the half cell. 1.00M solutions, 1 atm pressure, and 25°C are the standard conditions.
Electrochemical Series Table
|Element||Electrode Reaction||E° (volts)|
|Li||Li+(aq) + e– —> Li (s)||-3.05|
|K||K+(aq) + e– —> K(s)||-2.925|
|Ca||Ca2+(aq) + 2e– —> Ca(s)||-2.87|
|Na||Na+(aq) + e– —> Na(s)||-2.714|
|Mg||Mg2+(aq) + 2e– —> Mg(s)||-2.37|
|Al||Al3+(aq) + 3e– —> Al(s)||-1.66|
|Zn||Zn2+(aq) + 2e– —> Zn(s)||-0.7628|
|Fe||Fe2+(aq) + 2e– —> Fe(s)||-0.44|
|Pb||Pb2+(aq) + 2e– —> Pb(s)||-0.13|
|H||2H+(aq) + 2e– —> H2(g)||0|
|Cu||Cu2+(aq) +2 e– —> Cu(s)||+0.34|
|Ag||Ag+(aq) + e– —> Ag(s)||+0.80|
|Au||Au3+(aq) + 3e– —> Au(s)||+1.50|
Electropositive and Electronegative- Electrochemical Series of Metals
Electropositive elements (other than hydrogen) are those that have a higher tendency to lose electrons to their solution. Electronegative elements, on the other hand, are those that gain electrons. They are commonly found after the element hydrogen in the periodic table. In any event, we can figure out the order in which metals will replace one another from their salts by looking at the electrochemical series. As a result, electropositive metals are commonly used to replace hydrogen in acids.
Application of Electrochemical Series for NCERT Class 12
Identification of Oxidizing and Reducing agents
The electrochemical series aids in the identification of a good oxidising or reducing agent. All of the substances at the top of the electrochemical series are good oxidising agents, meaning they have a positive standard reduction potential, whereas those at the bottom of the electrochemical series are good reducing agents, meaning they have a negative standard reduction potential. F2, for example, is a strong oxidising agent with a standard reduction potential of +2.87 volts, while Li+ is a strong reducing agent with a standard reduction potential of -3.05 volts.
Calculating EMF of a Electrochemical Cell
The total of the standard reduction potentials of the two half cells is the cell’s standard emf: Half-cells for reduction and oxidation
Eocell = Eored + Eoox
The standard oxidation potential is always represented in terms of reduction potential, as is customary.
- standard oxidation potential (Eoox) = – standard reduction potential (Eored )
- Eocell = standard reduction potential of reduction half-cell – standard reduction potential of oxidation half-cell
Because, The anode undergoes oxidation, while the cathode undergoes reduction. Hence,
- Eocell= Eocathode– Eoanode
Predicting the Feasibility of Redox Reaction
If the free energy change (G) is negative, any redox reaction will occur spontaneously. The following is how the free energy is related to the cell emf:
ΔGo = nFEo
The number of electrons involved is n, the Faraday constant is F, and the cell emf is Eo.
- If Eo is positive, Go can be negative.
- The cell response is spontaneous when Eo is positive, and it acts as a source of electrical energy.
- If the result is negative, the spontaneous reaction will not be possible.
While determining the stability of a metal salt solution when stored in another metal container, the consequent value of Eo for redox reaction is crucial.
Anticipation of the Product
If there are 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 standard reduction potential (stronger oxidising agent) is discharged first at the cathode. When an aqueous solution of NaCl containing Na+, Cl-, H+, and OH- ions is electrolyzed, the H+ ion is preferentially deposited at the cathode (reduction) rather than the Na+ ion, since hydrogen’s reduction potential (0.00 volt) is larger than sodium’s reduction potential (0.00 volt) (-2.71 volt). The anion with the lowest reduction potential will be oxidised at the anode where oxidation takes place. As a result, OH-, which has a standard reduction potential of 0.40 volt, will be oxidised first, followed by Cl-, which has a standard reduction potential of 1.36 volt.
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Electrochemical Series- FAQs
Q. What is an electrochemical series?
Ans. A succession of electrochemical reactions or activities The electrochemical or electromotive series is formed when the electrodes (metals and nonmetals) in contact with their ions are ordered according to the values of their standard reduction potentials or standard oxidation potentials.
Q. How is the electrochemical series arranged?
Ans. Various redox equilibria are arranged in order of their standard electrode potentials to form the electrochemical series (redox potentials). The electrochemical series is ordered with the most negative E° values at the top and the most positive at the bottom.
Q. What is EMF series?
Ans. The electromotive force series (EMF series) is a rating system for metals based on their inherent reactivity. The metals at the top of the sequence are thought to be the noblest, as they have the largest positive electrochemical potential.
Q. What are the advantages of electro chemical series?
Ans. The electrochemical series aids in the identification of compounds that are good oxidising and reducing agents. The species above hydrogen in an electrochemical series are more difficult to reduce, and their typical reduction potential values are negative.
Q. Is electrochemical series and reactivity series Same?
Ans. The main distinction between electrochemical and reactivity series is that electrochemical series specifies the sequence of standard electrode potentials, whereas reactivity series specifies the arrangement of metals in descending order of reactivity.