Redox Reactions and Electrode Processes

Electrode Potential and Standard Electrode Potential are key concepts in the field of electrochemistry which is the branch of chemistry that deals with relationships between electric potential differences and observable chemical change. Electrode Potential is also used extensively in the development of sustainable battery technologies, as all modern-day batteries work on this principle to create voltage for the smooth operations of electronic gadgets. This article deals with the topic of Electrode Potential and Standard Electrode Potential in detail and helps us understand how electricity or potential is produced using chemistry.

When in any reaction, both process i.e., oxidation and reduction; happens simultaneously, that reaction is called a redox reaction. 

For example, in zinc-copper cell 

Oxidation Half-Reaction at Anode

Zn(s) → Zn²⁺+2e^–

Reduction of Half-Reaction at Cathode

Cu²⁺+2e^– → Cu(s)

To make metallic copper, zinc loses electrons that are grabbed by copper ions. The entire redox reaction between zinc and copper is:

Cu²⁺+ Zn(s) → Cu(s) + Zn²⁺

The Redox Process in Zinc and Copper Cells was observed.

In each half-cell, electrons move between the electrodes through the electrolyte. This movement of charge creates a potential known as Electrode Potential. Electrode Potential can be categorized into two types: Oxidation Potential and Reduction Potential. Let’s understand each of them:

Oxidation Potential: It represents the tendency of a metal (M) to undergo oxidation by losing electrons (ne^–) and forming metal ions (Mⁿ⁺). This process is denoted as

M → Mⁿ⁺ + ne^–.

Reduction Potential: It represents the tendency of metal ions (Mⁿ⁺) to gain electrons (ne^–) and convert them back into the original metal (M). This process is denoted as

Mⁿ⁺ + ne^– → M.

Factors Affecting Electrode Potential

There are various factors affecting the electrode potential, some of those factors are as follows:

• Nature of Electrolyte: The presence and concentration of ions in the solution affect the activity or effective concentration of the species involved in the redox reaction, thus impacting the electrode potential.
• Temperature: As temperature increases, the kinetic energy of the reacting species also increases, leading to faster reaction rates. The Nernst equation represents the changes in temperature that can affect the overall electrode potential.

Learn more about Nernst Equation.

• Pressure: For gaseous electrode reactions, increasing the pressure increases the concentration of the gaseous species, which alters the electrode potential accordingly.
• Surface Area of Electrode: A larger surface area provides more sites for redox reactions to occur, resulting in an increased electrode potential and a larger surface area of the electrodes also makes the transfer of electrons more efficient.
• pH and Concentration of Electrolyte: pH of the electrolyte solutions affects electrode potential, especially for those electrodes which involve hydrogen ions. Changing pH is nothing but a change in the concentration of hydrogen ions, and a change in concentration changes the rate of reaction.

The electrode potential can be calculated using the following formula:

E^∘_cell = E^∘_red – E^∘_oxid

The half-cell with the larger reduction potential goes through the reduction process, whereas the half-cell with the lower reduction potential goes through the oxidation process.

As we already discussed that the potential difference between the metal and its solution is known as the electrode potential. If the concentration of the participating species in the electrode reaction is unity and the reaction occurs at 298K and 1 atm pressure, the electrode potential is referred to as Standard Electrode Potential (E⁰).

How to measure Standard Electrode Potentials?

The standard electrode potential (E⁰) of hydrogen gas, in the case of the convention, is 0.00 volts. The redox couple is a stronger reducing agent than the H⁺/H₂ couple when the standard electrode potential is negative. On the other hand, a positive standard electrode potential suggests that the redox couple is a weaker reducing agent than the H⁺/H₂ pair.

There are various use cases for electrode potential and standard electrode potential, some of these use cases are as follows:

• It may be used to investigate processes like corrosion and pitting, as well as control the reaction process.
• The Electrode Potential can be used to help choose materials and equipment for reaction control.
• Corrosion caused by electrochemical and chemical reactions and processes can be predicted with this tool.

Also, Check

• Examples of Redox Reactions in Everyday Life
• Balancing Redox Reactions
• Standard Electrode Potential

Question 1:  What processes are involved in redox reactions?

Answer:

A redox process is an electron transfer reaction that involves both reduction and oxidation, with reduction being the intake of electrons and oxidation being the release of electrons.

Question 2: How does a redox reaction produce electricity?

Answer:

A galvanic cell, also known as a Voltaic cell, is an electrochemical cell that generates electrical energy through a redox reaction or redox process. A voltaic cell is made up of two half-cells that perform either the reduction or oxidation processes.

Question 3: How Electrolysis is an example of a redox reaction?

Answer:

Electrolysis is a redox reaction because reduction occurs at the cathode and oxidation occurs at the anode, and both of these reactions occur at the same time.

Question 4: What does the reduction process do?

Answer:

Chemical entities lose electrons during the reduction process, lowering their oxidation number. The oxidation part of the reaction involves the loss of electrons. Reduction is the polar opposite of oxidation.

Cu²⁺+2e^– → Cu(s)

Question 5: What is a redox couple example?

Answer:

In redox reactions, a redox pair is formed by the oxidised and reduced versions of each reactant. Redox couples are denoted as “Ox/red.” For example- Cu²⁺/Cu and Zn²⁺/Zn, have an oxidised version on the left and a reduced version on the right, separated by a slash.

Question 6: What are the uses of electrode potential?

Answer:

• It helps with corrosion and pitting investigations, as well as reaction control.
• Electrode Potential can be used to help choose materials and equipment for reaction control.
• Corrosion caused by electrochemical and chemical reactions and processes can be predicted with the help of this programme.

What is Electrode Potential?

Electrode potential is the measure of tendency of an electron to undergo a reduction or oxidation reaction, due to this fact it is also called redox potential.

What does Electrode Potential represent?

Electrode Potential represents the potential difference between an electrode and its surrounding solution when no current is flowing through the electrode.

How is Electrode Potential measured?

Electrode potential is measured using a reference electrode which has known and stable potential. To measure electrode potential

is typically measured using a reference electrode, which has a known and stable potential. The reference electrode is connected to the electrode of interest, and the potential difference between the two electrodes is measured using a voltmeter or a potentiostat.

What is standard electrode potential?

Standard electrode potential is the potential difference between an electrode and its surrounding solution when the concentration of all species involved in the electrode reaction is 1 M, the temperature is 25°C (298 K), and the pressure is 1 atm. Standard electrode potentials are tabulated and used as reference values to compare the reactivity of different electrodes which is known as electrochemical series.

How are standard electrode potentials determined?

Standard electrode potentials are determined experimentally by measuring the electrode potential of a half-cell relative to a reference electrode under standard conditions. The half-cell reaction is balanced, and the potential is measured using a voltmeter. The measured potentials are then tabulated, and the values are standardized and widely accepted.

What is the significance of standard electrode potential?

Standard electrode potentials provide valuable information about the reactivity and relative strength of different redox couples or half-reactions. By comparing the standard electrode potentials of different electrodes, it is possible to predict the direction of electron flow in a redox reaction and determine the feasibility of a particular redox process.

How is the direction of electron flow determined using standard electrode potentials?

The direction of electron flow in a redox reaction can be determined by comparing the standard electrode potentials of the half-reactions involved. The reaction will occur spontaneously in the direction where the more positive electrode potential corresponds to reduction (gaining electrons), and the more negative electrode potential corresponds to oxidation (losing electrons).

What does a positive or negative standard electrode potential indicate?

A positive standard electrode potential (E° > 0) indicates that the reduction half-reaction is more favorable under standard conditions, and the electrode acts as a good oxidizing agent. A negative standard electrode potential (E° < 0) indicates that the oxidation half-reaction is more favorable under standard conditions, and the electrode acts as a good reducing agent.

How does temperature affect electrode potential?

Electrode potential is temperature-dependent. As temperature increases, electrode potentials generally change according to the Nernst equation, which relates the electrode potential to the concentration and activities of the species involved in the redox reaction. The Nernst equation allows for the calculation of the electrode potential under non-standard conditions.

Can electrode potential be altered or controlled?

Electrode potential can be altered or controlled by changing the concentration of reactants or by applying an external potential using an external power supply. These changes can shift the electrode potential away from its standard value and allow for the manipulation of redox reactions.