EMF: Types and It’s Electrode Potential

Introduction to Cellular EMF

An electrochemical cell is a device that uses a chemical reaction to generate electricity. A device that transforms chemical energy into electrical energy is known as a chemical energy converter. An electrochemical cell can only function if there is a chemical reaction that involves the exchange of electrons. Redox reactions are the name for these types of reactions.

The voltage of a cell is what distinguishes it. Regardless of cell size, a certain type of cell generates the same voltage. If the cell is operated under ideal conditions, the chemical composition of the cell is determined by the cell voltage. Several factors, such as temperature differences, changes in concentration, and so on, can cause variations in cell voltage.

The EMF value of a specific cell can be calculated using Walther Nernst’s Nernst equation, which also provides the cell’s standard cell potential.

Electrode Potential Types

Let us quickly review the definition of electrode potential before moving on to the different types of electrode potential. If we immerse a piece of metal in a solution containing its ions, the metal will take on a positive or negative charge. Taking this into account, a certain or definite potential difference between the metal and the solution will develop. The electrode potential is the potential difference that is created.

We’ll also look at several examples to help us better understand the notion. When copper is dissolved in a solution containing Cu2+ ions, it gains a positive charge in relation to the solution. Between the copper plate and the solution, a potential difference is created. The electrode potential of copper is the result of this potential difference.

Similarly, if we immerse a zinc plate in a solution containing Zn2+ ions, the plate will acquire a negative charge in relation to the solution. Between the zinc plate and the solution, a potential difference has now been established. As a result, the potential difference is referred to as the zinc electrode potential.

After that, we’ll have a look at the various sorts of electrode potential.

When a metal rod is immersed in its salt solution, we usually detect two primary modifications. Oxidation and reduction will occur.

When we talk about oxidation, we’re talking about the passage of metal ions from the electrode into the solution. Electrons that aren’t needed are left behind. As a result, the electrode acquires a negative charge. Electrolytic solution pressure is the tendency of a metal to convert into ions.

Metal ions in solution, on the other hand, have a tendency to gain electrons from the electrode during reduction. As a result, the electrode acquires a positive charge. Due to the accumulation of metal ions on the metal surface, the metal gains a positive charge.

In both circumstances, though, a possible difference is established.

Meanwhile, the magnitude of a metal’s electrode potential can be described as a measure of the relative tendency to undergo oxidation or reduction in simple terms.

So, when it comes to the different forms of electrode potential, we can state that whether the metal electrode loses or gains electrons is purely determined by the composition of the metal electrode. As a result, there are two types of electrode potential:

Potential for Oxidation

Oxidation happens when an electrode is negatively charged in relation to the solution or when it functions as an anode.

Potential for Reduction

When the electrode has a positive charge in relation to the solution or when it behaves as a cathode. After that, there is a reduction.

Cell Electrochemical

An electrochemical cell is a device that may either generate electrical energy from a chemical reaction taking place inside it or use electrical energy supplied to it to allow a chemical reaction to take place inside it. These devices convert chemical energy to electrical energy and vice versa, and they’re used to power a variety of electronic items including TV remote controls and watches.

Galvanic or voltaic cells are cells that may create an electric current from chemical reactions that occur inside them.

Potential of an Electrode

The Electrode Potential is created by immersing a metal Electrode in a solution containing its ions, which causes a potential difference across the interface.

Consider the example of a zinc electrode that is oxidised by the emission of two electrons and released into solution when immersed in a zinc sulphate solution. A Potential difference is created by the presence of electrons in the Electrode and ions in the solution. Copper, on the other hand, has a favourable potential. The potential of these two cells when combined.

To find the Potential of a single half cell, you must first find a standard half cell with a known Potential value. Then, to ascertain the overall Potential, connect this standard half cell to an unknown half cell.

The difference between the Potentials of the two half cells makes up this total Potential. One example of a standard half-cell is the standard hydrogen electrode (SHE). SHE’s Potential Value is set to zero volts by default. Measure the potential difference between a conventional hydrogen Electrode and an unknown half-cell. The observed value is an unknown half-cell Potential difference because SHE is zero volts

A Cell’s EMF

The electromotive force of the cell, also known as the EMF, is the highest potential difference that exists between the two electrodes of a cell. The net voltage between the oxidation and reduction half-reactions is also known as this.

Electrochemical Cell Types

Galvanic Cell (Galvanic Cell)

A galvanic cell, also known as a voltaic cell, is a device that uses a spontaneous redox reaction to create electricity.

The reaction of zinc metal with aqueous copper sulphate solution is employed in this experiment.

Zn(s)+Cu2+(aq)→Zn2+(aq)+Cu(s)

It is made up of a zinc Electrode and a copper Electrode that have been bathed in zinc sulphate and copper sulphate solutions, respectively. The anode is the zinc electrode, and the cathode is the copper electrode. A zinc metal rod (anode) is immersed in a zinc sulphate solution in the container on the left. The copper rod (cathode) is immersed in a copper sulphate solution in the container on the right. The zinc and copper electrodes are connected by a copper connection. A salt bridge connects the solution in the anode and cathode compartments to the potassium sulphate solution.

In the anode compartment, the oxidation half-reaction occurs.

Zn(s)→Zn2+(aq)+2e−

The cathode reaction takes place as follows:

Cu2+(aq)+2e−→Cu(s)

Electrons are transferred from the zinc electrode to the copper cathode. Zn2+ is formed when zinc dissolves in the anode solution.

Cu2+ ions

In a cathode half cell, ions absorb electrons and transform them to Cu atoms. Simultaneously, SO42

Ions travel from the cathode half cell to the anode half cell through the salt bridge. Zn2+ is a similar case.

From the anode half cell to the cathode half cell, ions travel. Ions are transferred from one half-cell to the other to complete the circuit, ensuring a steady power source. The cell will keep running until either the zinc metal or the copper ions are depleted.

Daniel Cell 

It’s the same thing as a Galvanic Cell. The Copper-Zinc cell is also the same as the Galvanic Cell. The only difference is that Daniel’s cell can only use Zinc and Copper as Electrodes, whereas Galvanic cells can use a variety of metals as Electrodes.

The electrolytes used in the Daniel Cell are copper(II) sulphate and zinc sulphate, whereas the electrolytes used in the Galvanic Cell are the salts of metals of each Electrode.

Important point

Here are some of the most crucial things to keep in mind.

The absolute value of the single electrode potential cannot be directly measured.

Only the difference in potential between the two electrodes can be measured experimentally. We’ll need to couple the electrode with another electrode with a known potential, called a “reference electrode” in this case. The EMF of the resulting cell is calculated here.

The total of the potentials on the two electrodes equals the cell’s EMF. It can be expressed as follows:

EAnode + ECathode = Oxidation potential of anode + Reduction potential of cathode = Cell Emf

Conclusion

Electromotive force (EMF) is a term that simply refers to the electrical activity produced by a non-electrical source. It can be shown that gadgets generate emf by transforming one form of energy into another. The maximum potential difference between the two electrodes of a voltaic or galvanic cell is referred to as EMF in chemistry. Electrochemical cells, thermoelectric devices, solar cells, electric generators, and transformers are examples of devices that can generate an emf.