Standard Electrode Potential - Definition, Cell Potential with FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:51 PM IST

What is Electrode Potential?

Defining the electrode potential according to IUPAC is defined as the electromotive force that is built by the electrodes of two cells in electrochemistry. It can be represented by the letter “E”. It is impossible to calculate directly the value of single potential accurately and more precisely. By experiments it is the only method to measure the difference in potentials of two cells. While doing any experiment for calculating the value of potential one electrode is required with known potential that is termed as Reference potential and other one is unknown potential. Electrode potential depends on direction of flow of electrons, it does not depend on which electrode is working whether it is cathode or anode. It will also depend basically on three factors.

This Story also Contains

What is Electrode Potential?
Measurement of Electrode Potential:
Cell Potential:
What is standard electrode potential?
Standard Electrodes:
Single Electrode Potential:
Half-Cell Potential:

Electrolytic concentration
Pressure
Temperature

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Measurement of Electrode Potential:

The measurement of electrode potential can be done when it is connected to a standard hydrogen electrode which constitutes a cell.
The electrode which is showing negative electrode is termed as negative terminal whereas electrode which is showing positive electrode termed as positive terminal.
The potential difference that is developed between positive and negative terminals is measured by potentiometer.
Through Galvanometer we can identify the direction of flow of electric current outside the electric circuit.
This helps in identifying the anode and cathode as the electrons will flow opposite to current which means in direction from anode to cathode.
In Daniel cell,

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The reaction at Anode will be an oxidation reaction i.e. loss of electrons.

Zn→Zn²⁺+2e^-

The reaction at cathode will be a reduction reaction i.e. gain of electrons.

Cu²⁺+2e^-→Cu

The net reaction will be the addition of two half reactions of cathode and anode.

Zn+Cu²⁺Zn²⁺+ Cu

Where E_cathode=0.34V, E_anode=-0.76VA

Emf of cell= E_cell=E_cathode-E_anode

E_cel_l=0.34--0.76

V=1.10

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Cell Potential:

The measurement of cell potential can be done by the measurement of potential difference between the two half-cell in electrochemical cell. The reaction between two electrodes are redox reaction so electrons move easily. Cell potential can be measured in terms of voltage(V), which gives a certain value of cell potential.

What is standard electrode potential?

Standard electrode potential is being used for the measurement of potential at an equilibrium condition. The difference is found between electrode and electrolyte. Such a difference is called the potential of electrodes. When the concentration of all the species in a semi cell is found as unity or at equilibria condition such type of potential is called standard electrode potential.

Define Standard Electrode Potential:

In an electrochemical cell at standard terms and conditions, with pressure at 1 atm, temperature298k and concentration of the cell is 1M such type of potential is called standard electrode potential. It is symbolically represented as E°cell, which represents the standard electrode potential. It can also be defined as the half-reaction that is measured by standard hydrogen electrodes at standard conditions.

Measurement of Standard electrode potential:

While taking an example of Standard electrode potential we can determine the vale of potential using two electrodes one is hydrogen electrode and other is zinc electrode and they are connected by salt bridge and high resistance voltmeter are attached to both the electrodes. All the conditions such as temperature, pressure, concentration are kept standard to measure the standard electrode potential.

The measurement is taken as according to reference electrodes which are standard electrodes of hydrogen. The standard electrode potential of a reference electrode (hydrogen) is 0 volts.
The measurement of standard electrode potential can be done by pairing it with a reference electrode and checking the results of galvanic cell.
It is to be noted that change in temperature, pressure or concentration changes the potential of the cell.
The measurement of standard electrode potential can be done with the help of two half cells or by half-reactions that is represented below:

E^°_cell=E^°_cathode-E^°_anode

It can be used to measure the relative strength of various reductants and oxidants.

Standard Electrodes:

When we define the electrodes which are an important component of every electrochemical cell. Standard electrodes are the point where current flows i.e. enters the electrode and leaves the electrode when it enters the electrode it is denoted as anode and when it leaves the electrode it is denoted as cathode. The electric charge is developed by the transfer of electrons from one half-cell to another half-cell. The charge is basically based on the factors of standard electrode potential with reference potential of 0 volts.

Standard Reduction Potentials:

Standard reduction potential can be defined as a species which get reduced. It can be represented in the form of reduction half reactions. Here we take an example showing you a generic element “A” and C will be the charge.

Now taking an example of standard reduction potentials where E^°=+0.340A for reaction.

Standard reduction potential for copper can be represented as follows:

Cu²⁺+2e^-→Cu

Standard Oxidation Potentials:

Standard oxidation potential is likely to be much similar with standard reduction potentials, it is the species which gets oxidised at given standard conditions. It can also be written in the form of half reaction. At standard condition general form of reaction is written below:

A(s)A^c++Ce^-

Standard oxidation potential for copper can be represented as follows:

Cu(s)Cu²⁺+2e^-

E₀^°(SOP)=-0.34V

It is to be noted that standard reduction potential and standard oxidation potential are opposite to each other in relation to sign for the same chemical species.

Relation in between standard oxidation potential (SOP) and standard reduction potential (SRP) is as follows:

E₀^°(SRP)=-E₀^°(SOP)

Also, students can refer,

Single Electrode Potential:

While defining the single electrode potential we must understand the basic requirements of electrochemical cell, and how they work. Electrochemical cell is basically consist of two half-cells, with open circuit. The two metal electrodes are placed where the ions are transferred into solution. Due to transfer of the ion single electrode will develop the potential with respect to the solution in half cell, such potential is termed as Single electrode potential.

As in the case of Daniel cell the electrodes are not connected externally so positive and negative charge develops on anode and cathode respectively. On anodeZn/Zn²⁺ negative charge will developed and on cathodeCu/Cu²⁺, positive charge will be developed so to determine the single electrode potential in such a situation an amount of charge on individual electrodes has been taken.

The single electrode potential will depend on the following factors such as:

Tendency of making ions
Temperature
Concentration of ions present in the solution

Half-Cell Potential:

Half-Cell Potential can be defined as potential which is developed at each individual electrode in an electrochemical cell. Overall potential can be calculated by the two-half cell in an electrochemical cell. The measurement ogf half-cell is used to help in evaluating the:

Presence of Corrosion
Vulnerability of the area of corrosion

The half-cell will give only the predicted probability of area prone to corrosion at given short period of time but long-term monitoring is way more necessary for prediction of severity of corrosion.

The potential difference is associated with each electrode and the magnitude of potential will depend on the nature of the individual electrode and also on the concentration of solution. The sign will depend on the direction of reaction in which it proceeds. The half-cell method is cheaper and non-destructive in order to predict the corrosion risk. Therefore, the potential of half-cell is directly proportional to the chances of occurrence of corrosion.

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NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. What is a reversible electrode?

Reversible electrodes are those electrodes that will readily dissolve, when a current is passed from the metallic electrode, and have plated on it metal, when the current will pass but in opposite or reverse direction.

2. What do you mean by the term SRP in chemistry?

The SRP is the short form of standard reduction potential. It is the reduction potential of a molecule which is found under certain specific standard conditions. It can help in determining the directionality of reaction.

3. How would you find the electrode potential of copper?

Standard electrode potential of copper for galvanic cells is 0.34V.

4. How can you increase the reduction potential?

To increase the reduction potential of an electrode by just increasing the metal cation concentration in the solution or by increasing the temperature.

5. How do standard electrode potentials help in determining the feasibility of a redox reaction?

Standard electrode potentials can be used to calculate the standard cell potential of a redox reaction. If the resulting cell potential is positive, the reaction is thermodynamically favorable (spontaneous) under standard conditions.

6. How does the concept of standard electrode potential apply to fuel cells?

In fuel cells, standard electrode potentials help determine the maximum theoretical voltage that can be produced. The difference between the reduction potentials of the fuel oxidation at the anode and the oxidant reduction at the cathode gives the cell's theoretical voltage.

7. Can standard electrode potentials be used to predict the direction of electron flow in a galvanic cell?

Yes, standard electrode potentials can predict the direction of electron flow in a galvanic cell. Electrons will flow from the electrode with the more negative potential (anode) to the electrode with the more positive potential (cathode).

8. How do standard electrode potentials relate to the reactivity series of metals?

The reactivity series of metals is directly related to their standard electrode potentials. Metals with more negative standard electrode potentials are more reactive and appear higher in the reactivity series.

9. How does pH affect standard electrode potentials?

pH can significantly affect standard electrode potentials, especially for reactions involving H+ or OH- ions. The Nernst equation can be used to calculate the potential at different pH values, showing how it changes with hydrogen ion concentration.

10. How does the concentration of ions affect electrode potential?

The concentration of ions affects electrode potential according to the Nernst equation. As the concentration of reactants increases, the electrode potential becomes more positive for reduction reactions and more negative for oxidation reactions.

11. Can the standard electrode potential of a half-cell be measured directly?

No, the standard electrode potential of a single half-cell cannot be measured directly. It can only be determined relative to another half-cell, typically the standard hydrogen electrode.

12. How does the electrochemical series help predict the direction of redox reactions?

The electrochemical series, which lists standard electrode potentials in order of decreasing reduction potential, helps predict the direction of redox reactions. Species with more positive potentials will oxidize those with more negative potentials.

13. What is the difference between standard electrode potential and standard reduction potential?

There is no difference between standard electrode potential and standard reduction potential. Both terms refer to the same concept: the potential of a half-cell measured against the standard hydrogen electrode under standard conditions.

14. What is the relationship between standard electrode potential and Gibbs free energy?

The standard electrode potential is directly related to the Gibbs free energy of the reaction. The relationship is given by the equation ΔG° = -nFE°, where n is the number of electrons transferred, F is Faraday's constant, and E° is the standard cell potential.

15. What is the significance of the standard electrode potential in determining the strength of oxidizing and reducing agents?

The standard electrode potential indicates the strength of oxidizing and reducing agents. Species with more positive reduction potentials are stronger oxidizing agents, while those with more negative reduction potentials are stronger reducing agents.

16. What is the significance of the standard electrode potential in determining the decomposition voltage of an electrolyte?

The decomposition voltage of an electrolyte is related to the difference in standard electrode potentials of the reactions occurring at the anode and cathode. It represents the minimum voltage required to initiate electrolysis.

17. How do standard electrode potentials help in understanding the concept of galvanic corrosion?

Standard electrode potentials explain galvanic corrosion by predicting which metal in a galvanic couple will corrode preferentially. The metal with the more negative potential will act as the anode and undergo oxidation (corrosion).

18. What is the role of standard electrode potentials in the design of reference electrodes?

Standard electrode potentials are essential in designing reference electrodes. Ideal reference electrodes have stable and well-defined potentials, often based on redox couples with known standard potentials.

19. How do standard electrode potentials relate to the concept of electrochemical machining?

In electrochemical machining, standard electrode potentials help in selecting appropriate electrode materials and electrolytes. The potential difference between the workpiece and the tool electrode drives the material removal process.

20. What is the significance of the potential of zero charge in relation to standard electrode potentials?

The potential of zero charge is the potential at which the electrode surface has no excess charge. It's important in understanding the behavior of electrodes at potentials different from their standard electrode potentials, particularly in electrochemical double layer formation.

21. How does complexation affect standard electrode potentials?

Complexation can significantly alter standard electrode potentials by stabilizing certain oxidation states of metal ions. This can lead to shifts in the potential, often making it more positive for reduction reactions.

22. What is overpotential and how does it relate to standard electrode potentials?

Overpotential is the additional potential beyond the thermodynamically determined electrode potential needed to drive a reaction at a certain rate. It represents the kinetic limitations of the electrode reaction and is not accounted for in standard electrode potentials, which are thermodynamic values.

23. What is the role of standard electrode potentials in electroplating processes?

Standard electrode potentials guide the selection of appropriate electrodes and electrolytes in electroplating. The metal to be plated should have a more positive reduction potential than the substrate to ensure successful deposition.

24. What is the difference between standard electrode potential and formal potential?

Standard electrode potential is measured under standard conditions with activities of species equal to unity. Formal potential is measured under non-standard conditions and takes into account the actual concentrations and activity coefficients of the species involved.

25. Why is the standard hydrogen electrode used as a reference?

The standard hydrogen electrode (SHE) is used as a reference because it provides a universal baseline for comparing the potentials of different electrodes. Its potential is arbitrarily set to zero, allowing for consistent measurements across different electrochemical systems.

26. Can standard electrode potentials be used to predict the products of electrolysis?

Yes, standard electrode potentials can be used to predict the products of electrolysis. In an electrolytic cell, the species with the least negative (or most positive) reduction potential will be reduced at the cathode, while the species with the least positive (or most negative) oxidation potential will be oxidized at the anode.

27. How does the concept of standard electrode potential relate to battery design?

Standard electrode potentials are crucial in battery design as they help determine which combinations of electrodes will produce the highest cell potential. Batteries are designed to maximize the potential difference between the anode and cathode.

28. What is the significance of the standard state in electrode potential measurements?

The standard state (1 M concentration, 1 atm pressure, 25°C) provides a consistent reference point for comparing electrode potentials across different systems. This allows for the creation of standardized tables of electrode potentials that can be used universally.

29. How does the concept of standard electrode potential relate to corrosion?

Standard electrode potentials help explain and predict corrosion behavior. Metals with more negative standard electrode potentials are more likely to corrode in the presence of oxidizing agents or metals with more positive potentials.

30. What is the relationship between standard electrode potential and the equilibrium constant of a redox reaction?

The standard electrode potential is related to the equilibrium constant (K) of a redox reaction through the equation E° = (RT/nF) ln K, where R is the gas constant, T is temperature, n is the number of electrons transferred, and F is Faraday's constant.

31. How do standard electrode potentials help in understanding the Galvanic series?

The Galvanic series, which ranks metals according to their corrosion tendency in seawater, is closely related to standard electrode potentials. Metals with more negative potentials are higher in the series and more prone to corrosion.

32. How do standard electrode potentials relate to the concept of disproportionation?

Disproportionation reactions can be predicted using standard electrode potentials. If a species has two different oxidation states with standard electrode potentials that span zero, it may undergo disproportionation.

33. What is the role of standard electrode potentials in understanding electron transfer reactions in biological systems?

In biological systems, standard electrode potentials help explain the direction and feasibility of electron transfer reactions, such as those in the electron transport chain. They provide insight into which molecules can serve as electron donors or acceptors in metabolic processes.

34. How do standard electrode potentials relate to the concept of electronegativity?

There is a correlation between standard electrode potentials and electronegativity. Elements with higher electronegativity generally have more positive standard reduction potentials, indicating a greater tendency to gain electrons.

35. What is the standard electrode potential?

The standard electrode potential is the measure of the tendency of a chemical species to be reduced at an electrode under standard conditions (1 M concentration, 1 atm pressure, and 25°C). It represents the potential difference between an electrode and the standard hydrogen electrode, which is assigned a potential of zero volts.

36. How is cell potential related to standard electrode potentials?

The cell potential is calculated by subtracting the standard electrode potential of the anode (oxidation) from that of the cathode (reduction). Mathematically, E°cell = E°cathode - E°anode.

37. What is the significance of the sign (positive or negative) of the standard electrode potential?

The sign of the standard electrode potential indicates the direction of spontaneous electron flow. A positive value means the electrode has a greater tendency to be reduced than the standard hydrogen electrode, while a negative value indicates a greater tendency to be oxidized.

38. What factors influence the magnitude of the standard electrode potential?

The magnitude of the standard electrode potential is influenced by factors such as the nature of the species involved, their tendency to gain or lose electrons, and the stability of the products formed in the reaction.

39. How does temperature affect standard electrode potentials?

Temperature changes can affect standard electrode potentials by altering the equilibrium constant of the redox reaction. Generally, an increase in temperature leads to a decrease in the magnitude of the standard electrode potential.

40. How does the solvent affect standard electrode potentials?

The solvent can significantly affect standard electrode potentials by influencing the solvation of ions and the stability of species involved in the redox reaction. Different solvents can lead to different standard electrode potentials for the same redox couple.

41. Can standard electrode potentials be used to predict the products of a displacement reaction?

Yes, standard electrode potentials can predict the products of a displacement reaction. A metal with a more negative standard electrode potential will displace a metal with a more positive potential from its salt solution.

42. How do standard electrode potentials help in understanding the passivation of metals?

Standard electrode potentials can explain passivation phenomena. Some metals with negative standard potentials form stable oxide layers with more positive potentials, leading to passivation and increased corrosion resistance.

43. What is the relationship between standard electrode potentials and the electron affinity of elements?

There is a general correlation between standard electrode potentials and electron affinity. Elements with higher electron affinities tend to have more positive standard reduction potentials, reflecting their greater tendency to accept electrons.

44. How do standard electrode potentials relate to the concept of redox titrations?

In redox titrations, standard electrode potentials help in selecting appropriate indicators and predicting the feasibility and endpoint of the titration. The potential difference between the titrant and analyte determines the sharpness of the endpoint.

45. What is the significance of standard electrode potentials in electrochemical sensors?

Standard electrode potentials are crucial in designing electrochemical sensors. They help in selecting appropriate electrode materials and predicting the sensor's response to different analytes based on their redox potentials.

46. How do standard electrode potentials relate to the concept of electrochemical impedance?

While standard electrode potentials primarily deal with thermodynamics, they influence electrochemical impedance by affecting the equilibrium state of the electrode-electrolyte interface, which in turn affects the system's response to small perturbations.

47. What is the significance of standard electrode potentials in understanding the Latimer diagrams?

Latimer diagrams use standard electrode potentials to represent the various oxidation states of an element. They help in predicting the stability of different oxidation states and the possibility of disproportionation reactions.

48. How do standard electrode potentials help in understanding the concept of electrochemical windows?

The electrochemical window of a solvent-electrolyte system is determined by the standard electrode potentials of the reactions that limit the stability of the system, such as solvent decomposition or electrolyte reduction/oxidation.

49. What is the relationship between standard electrode potentials and the ionization energy of elements?

There is a general inverse relationship between standard electrode potentials and ionization energies. Elements with lower ionization energies tend to have more negative standard reduction potentials, reflecting their greater tendency to lose electrons.

50. What is the significance of standard electrode potentials in understanding the behavior of amphoteric elements?

Standard electrode potentials can explain the amphoteric behavior of certain elements. These elements may have different standard potentials for reactions in acidic and basic conditions, leading to their ability to act as both acids and bases.

51. How do standard electrode potentials help in predicting the stability of oxidation states in transition metals?

Standard electrode potentials provide information about the relative stability of different oxidation states in transition metals. Larger potential differences between adjacent oxidation states generally indicate greater stability of the lower oxidation state.

52. What is the role of standard electrode potentials in understanding electrochemical gradient formation in biological membranes?

Standard electrode potentials help explain the formation and maintenance of electrochemical gradients across biological membranes. They provide insight into the energetics of ion transport and the generation of membrane potentials.

53. How do standard electrode potentials relate to the concept of electrochemical promotion of catalysis?

In electrochemical promotion of catalysis, standard electrode potentials help understand how applied potentials can modify the catalytic activity of electrode surfaces by altering the energetics of adsorption and reaction processes.

54. What is the significance of standard electrode potentials in the field of electrochemical energy storage?

In electrochemical energy storage devices like batteries and supercapacitors, standard electrode potentials are crucial for material selection and device design. They help determine the theoretical voltage and energy density of the storage system.