Galvanic Cell: Definition, Construction and Cell Reaction

Galvanic Cell: Cells and batteries are unquestionably useful and important. Cells are used in so many various ways in our daily lives. A Galvanic Cell or Voltaic Cell is an electrochemical cell that exists alongside other cells. It converts the chemical energy of spontaneous redox reactions into electrical energy. A galvanic cell is an example of how energy can be collected through simple reactions between a few elements. In this article, we have discussed everything about galvanic cells including galvanic cell definition, Daniell cell and Leclanche cell,

To facilitate balancing the overall equation for Galvanic cells and emphasising the actual chemical transformations, it is often advantageous to divide the oxidation-reduction reactions into half-reactions when formulating the equations. Read this article to know galvanic cell definition, construction and more.

Galvanic Cell Definition

A device used to convert chemical energy produced in a redox reaction into electrical energy is called a galvanic cell.
It is named after the name of scientist Luigi Galvani. Galvani cell is also called a voltaic cell, named after the scientist Alessandro Volta. Some common examples of galvanic cells are the Volta cell, Daniel cell, Leclanche cell, dry cell, etc.

Constructions of Galvanic Cell

A galvanic cell is constructed by combining an oxidation electrode with a suitable reduction electrode to convert chemical energy into electrical energy by a redox reaction. Two electrolytic solutions, in which electrodes are immersed are connected to each through a porous diaphragm or a salt bridge. The two electrodes are connected to a device that utilizes the electrical energy produced in the outer circuit.

Electrons get liberated i.e., oxidation occurs at the oxidation electrode.  These electrons accumulate on the electrode and provide a negative potential. At the reduction electrode, a positive potential develops on account of the reduction process occurring at it. When these two electrodes are connected, electrons start flowing from the oxidation electrode to the reduction electrode in the outer circuit due to a difference in potential between them. Thus, an electric current is produced.

The electrode at which the oxidation process occurs is called the anode, while the one at which the reduction process takes place is called the cathode. In a galvanic cell, the anode has a negative polarity and the cathode has a positive polarity.

What is Salt Bridge?

A salt bridge is a U- shaped tube containing a concentrated solution of an inert electrolyte like \( {\text{KCl}}\), \( {\text{KN}} { {\text{O}}_3}\), \( { {\text{K}}_2} {\text{S}} { {\text{O}}_4}\), etc., or solidified solution of such an electrolyte in Agar-Agar and gelatin. These inert electrolytes do not take part in the reduction reaction.

The function of the salt bridge is to allow the movement of ions from one solution to the other without mixing two solutions. Thus, whereas electron flow in the outer circuit in the wire, and the inner circuit is completed by the flow of ions from one cell to the other through the salt bridge. The salt bridge maintains the electrical neutrality of the solution in the two half-cells.

How Daniel Cell is a Galvanic cell?

Daniel cell is the best example of a galvanic cell. The anode of the Daniel cell consists of a zinc rod dipped in the solution of zinc sulphate \(\left({{\text{ZnS}} { {\text{O}}_ {\text{4}}}} \right)\) of concentration \( { {\text{C}}_1}\). The cathode is made by immersing a copper rod in the solution copper sulphate \(\left({{\text{CuS}} { {\text{O}}_ {\text{4}}}} \right)\) of concentration \( { {\text{C}}_2}\). The \( {\text{Z}} { {\text{n}}^ { {\text{2 + }}}}\) and \( {\text{C}} { {\text{u}}^ { {\text{2 + }}}}\) ions in the solution are made in electrical communication either by direct contact or through a salt bridge.

The zinc electrode acts as an anode at which oxidation takes place and the copper electrode acts as a cathode at which reduction occurs. Since electrons are produced at the zinc electrode, this electrode is rich in electrons and pushes the electron into the external circuit. Conversely, the electron-deficient copper electrode pulls the electron from the external circuit. Thus, electrons flow from zinc electrode to copper electrode.

What is the Mechanism of Production Electric Current in the Galvanic Cell?

The chemical reaction responsible for the generation of electric current from chemical energy in a galvanic cell is a redox reaction. This redox reaction is called the cell reaction of the given galvanic cell.
A galvanic cell is composed of two half cells, i.e., oxidation half cell and reduction half cell. The oxidation occurs at the oxidation electrode, i.e., at the anode, and involves the liberation of electrons. The reduction occurs at the reduction electrode, i.e., at the cathode, and involves the gain of electrons. The cell reaction is obtained by adding oxidation and reduction half-reactions of Daniel cell.

At the anode, oxidation half cell reaction: \( {\text{Zn}} \to {\text{Z}} { {\text{n}}^ { {\text{2 + }}}} {\text{ + 2}} { {\text{e}}^ {\text{-}}}\)
At the cathode, reduction half cell reaction: \( {\text{C}} { {\text{u}}^ { {\text{2 + }}}} {\text{ + 2}} { {\text{e}}^ {\text{-}}} \to {\text{Cu}}\)
The cell reaction (redox reaction): \( {\text{Zn + C}} { {\text{u}}^ { {\text{2 + }}}} \to {\text{Cu + Z}} { {\text{n}}^ { {\text{2 + }}}}\)
This reaction is responsible for the generation of electricity in the Daniel cell.

How to Represent a Galvanic Cell?

1. An oxidation and reduction half-cells are represented by putting a single vertical line between the symbols of metal acting as an electrode and the symbol of ion present in the electrolyte in contact with metal. The vertical line represents the phase boundary.
2. In the oxidation half cell, the reduced half is written on the left, whereas in the reduction half cell, the reduced state is written on the right.
3. The molar concentration of the solution is written in the parenthesis after the formula of the ion.
\(\begin{array}{*{20}{c}} {\mathop {\left. {\rm{M}} \right|{{\rm{M}}^{{\rm{n + }}}}({\rm{aq}})}\limits_{({\rm{Oxidation}}\,{\rm{half}})} }&{amp;\mathop {{{\rm{M}}^{{\rm{n + }}}}({\rm{aq}})\mid {\rm{M}}}\limits_{({\rm{Reduction}}\,{\rm{half}})} } \end{array}\)
4. The salt bridge that connects to the solution is represented by two parallel vertical lines, i.e., \(ǁ\).
Example: Cell representation of Daniel cell
Redox reaction occurring in the Daniel cell is \( {\text{Zn}} + {\text{CuS}} { {\text{O}}_4} \to {\text{Cu}} + {\text{ZnS}} { {\text{O}}_4}\)
Cell representation: \({\rm{Zn}}\left| {{\rm{Z}}{{\rm{n}}^{{\rm{2 + }}}}\left. {\left( {{{\rm{c}}_1}} \right)} \right\|{\rm{C}}{{\rm{u}}^{{\rm{2 + }}}}\left( {{{\rm{c}}_{\rm{2}}}} \right)} \right|{\rm{Cu}}\)

Difference Between Galvanic Cell and Electrolytic Cell

Based on the electrochemical changes occurring in electrochemical cells, electrochemical cells are divided into the galvanic cell and electrolytic cell. The difference between them is as follows:

Galvanic Cell Corrosion

The electrochemical erosion of metals is known as galvanic corrosion. When two different metals come into touch with each other in the presence of an electrolyte, such as saltwater, corrosion occurs. This results in the formation of a galvanic cell, with hydrogen gas developing on the more noble (less active) metal. The electrochemical potential generated then generates an electric current, which electrolytically dissolves the less noble substance.

Summary

In this article, you have explored the meaning, construction, working, and representation of Galvanic Cell in detail. You also learned how galvanic cell is different from the electrolytic cell.

FAQs on Galvanic Cell

Let’s see the commonly asked questions about Galvanic Cells:

Q.1. How does a galvanic cell work?
Ans: The chemical reaction responsible for the generation of electric current from chemical energy in a galvanic cell is a redox reaction. A galvanic cell is composed of two half cells, i.e., oxidation half cell and reduction half cell. The oxidation occurs at the oxidation electrode, i.e., an anode and it involves the liberation of electrons. The reduction occurs at the reduction electrode, i.e., a cathode and it involves the gain of electrons. This reaction is responsible for the generation of electricity.

Q.2. What is a galvanic cell? Explain with an example?
Ans: A device used to convert chemical energy produced in a redox reaction into electrical energy is called a galvanic cell. The Galvanic Cell demonstrates how energy can be harnessed through simple reactions between a few elements.
Example: In Daniel cell, electrical energy is produced by the redox reaction between copper sulfate and zinc sulfate solution.
Zn + Cu2 + →Cu + Zn2 +

Q.3. What is a galvanic cell used for?
Ans: Galvanic cells are used to convert chemical energy into electrical energy. This energy is used as a source of electricity.

Q.4. What are the basic features of a galvanic cell?
Ans: A galvanic cell is constructed by combining an oxidation electrode with a suitable reduction electrode to convert chemical energy into electrical energy by a redox reaction. Two electrolytic solutions in which electrodes are immersed are connected to each through a porous diaphragm or a salt bridge. In the outer circuit, the two electrodes are connected to a device that utilizes the electrical energy produced. The electrode at which the oxidation process occurs is called the anode, while the one at which the reduction process takes place is called the cathode. In a galvanic cell, the anode has a negative polarity, and the cathode has a positive polarity.

Q.5. What is a galvanic cell used for?
Ans: Galvanic cells are used to convert chemical energy into electrical energy. This energy is used as a source of electricity.

Q.6. What are the basic features of a galvanic cell?
Ans: A voltaic cell is constructed by combining an oxidation electrode with a suitable reduction electrode to convert chemical energy into electrical energy by a redox reaction. Two electrolytic solutions in which electrodes are immersed are connected to each through a porous diaphragm or a salt bridge. In the outer circuit, the two electrodes are connected to a device that utilizes the electrical energy produced. The electrode at which the oxidation process occurs is called the anode, while the one at which the reduction process takes place is called the cathode. In a galvanic cell, the anode has a negative polarity, and the cathode has a positive polarity.

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