Electrochemical Cell: Working Principle, Reaction

Electrochemical Cell: An electrolytic cell uses electrical energy to facilitate chemical reactions. They convert electrical energy to chemical energy. There are two types of electrochemical cell. They are Galvanic cell or Voltaic cell and Electrolytic cell.  Voltaic cells or Galvanic cells which is an example of  electrochemical cell convert Chemical energy to Electrical energy, Electrolytic cells convert Electrical energy to Chemical energy. 

Now that students know what is electrochemical cell, they should also be able to define electrochemical cells. This article will clarify this conceptual understanding among students. By the end of the article, they will be able to understand the difference between electrolytic cell and electrochemical cell. They will also be able to know about different electrochemical cell examples.

What is Electrochemical Cell?

An electrochemical cell is an apparatus or device that produces electric current from chemical change and energy released by this spontaneous redox reaction. Electrons are transferred from one chemical species to another; thus, an electric current is produced. Electrochemical cells convert chemical energy into electrical energy and vice versa.

An electrochemical cell is comprised of two half-cells. Each of them consists of an electrode and an electrolyte that can be the same or different in the two half cells. The main components of an electrochemical cell are:

1. Electrodes – The solid electrical conductor composed of good conductors such as metals in an electrochemical cell are known as electrodes. They are of two types:
   a. The Anode – The cell compartment where oxidation takes place.
   b. The Cathode – The cell compartment where reduction takes place.
2. Electrolyte – An electrolyte is a compound contained in between the electrodes that producely moving ions resulting in an electrically conducting solution when dissolved in polar solvents, such as water. 
3. Salt Bridge – This connects the oxidation half and reduction half of an electrochemical cell and completes the electrochemical circuit. It is filled with saturated salt solutions like \({\rm{KCl}}\). The bridge allows the ions in the solution to move from one half-cell to another, which is vital for the reaction to continue. A filter paper dipped in Potassium Nitrate or Sodium Chloride solution can act as an example of salt bridge.

Electrochemical Cell Example With Diagram

Electrochemical Cell Example

Electrochemical cells are used for various purposes in our daily life. Some examples of these cells or batteries are:

1. One of the most common examples of an electrochemical cell (galvanic cell) used in our daily life is a \(1.5\;{\rm{V}}\) cell.
2. Disposable AA batteries are used in a torch and remote controls.
3. Lithium-ion batteries are used in a wide range of tools such as UPS (Uninterruptible Power Supply), solar power storage systems, and most of our electronic gadgets such as earphones, mobile phones, tablets, laptops, and cordless power tools.

Types of Electrochemical Cell

Electrochemical cells are primarily of two types:

1. Galvanic cell or voltaic cell
2. Electrolytic cell

Let us learn about both of their key features and differences in tabular form:

Difference Between Electrolytic Cell and Electrochemical Cell

An electrochemical cell is a general term used for both galvanic or voltaic cells and electrolytic cells. Still, as the name signifies, electrochemical cells convert chemical energy into electrical energy and vice-versa. In comparison, electrolytic cells convert electrical energy into chemical energy by electrolysis.

An electrochemical cell can behave like an electrolytic cell when a potential difference that is greater than the potential difference of an electrochemical cell is applied. In this condition, the electric current begins to flow in the opposite direction; similarly, as in an electrolytic cell, the non-spontaneous reaction takes place.

Electrochemical Cell Reaction

A cell reaction describes the overall chemical change in an electrochemical cell. A cell reaction is facilitated by electrolytic cells, which are a class of electrochemical cells using electric currents. While writing the cell reaction corresponding to a cell diagram, the right-hand side half-reaction of the cell is written as reduction, and the left-hand side half-reaction is written as oxidation.

In this cell diagram, the electrochemical cell comprises copper and zinc metals with solutions of their sulphates \((0.1{\rm{M}})\) as electrolytes. In this process, electrons are transferred from the zinc which behaves as an anode to the copper which behaves as the cathode through an electrically conducting path and generate an electric current.

The overall cell reaction can be represented as:

Half-cell Reactions

(i) At Anode (Oxidation)
\({\rm{Zn}} \to {\rm{Z}}{{\rm{n}}^{2 + }} + 2{{\rm{e}}^ – }\)

(ii) At Cathode (Reduction)
\({\rm{C}}{{\rm{u}}^{2 + }} + 2{{\rm{e}}^ – } \to {\rm{Cu}}\)

Overall cell Reaction

\(\frac{{\begin{array}{*{20}{l}}{\begin{array}{*{20}{c}}{{\rm{Zn}} \to {\rm{Z}}{{\rm{n}}^{2 + }} + 2{{\rm{e}}^ – }}\\{{\rm{C}}{{\rm{u}}^{2 + }} + 2{{\rm{e}}^ – } \to {\rm{Cu}}}\end{array}}\end{array}}}{{{\rm{Zn}} + {\rm{C}}{{\rm{u}}^{2 + }} \to {\rm{Z}}{{\rm{n}}^{2 + }} + {\rm{Cu}}}}\)

Thus, through this overall cell reaction, it is clear that in this case, Zinc is undergoing oxidation, and Copper is undergoing reduction.

Electrochemical Cell Working

The working of electrochemical cells is explained below:

Principle of Working of Electrochemical Cell

1. The basic principle of working of an electrochemical cell is the transfer of electrons generated from a redox reaction occurring in it that results in the production of electric current.
2. Electrons are released from metals used as electrodes.
3. On losing electrons, metals get oxidised. On the other hand, if they gain electrons, they get reduced.
4. When such redox reactions occur, energy decreases and appear as electrical energy.

Define Electrochemical Cell: Working Mechanism

After the complete setup of an electrochemical cell, a deflection is observed in the external circuit’s galvanometer when the switch is put on. The needle of the galvanometer moves towards the beaker containing copper sulphate solution. It indicates that current has flown from the beaker containing copper sulphate solution to the beaker containing zinc sulphate solution. The change happens when the circuit gets completed and causes oxidation of zinc atoms of zinc electrode and reduction of copper atoms of copper rod. Zinc releases two electrons that get accepted by Copper via an external circuit. The complete redox reaction that occurs in the system is:
\({\rm{Zn}} + {\rm{C}}{{\rm{u}}^{2 + }} \to {\rm{Z}}{{\rm{n}}^{2 + }} + {\rm{Cu}}\).

Cell Reaction Representation

Electrochemical cell representation can be done by following the mentioned conventions recommended by the International Board of Chemistry:

1. Reduction half-reaction is represented as: \({\rm{C}}{{\rm{u}}^{2 + }}(0.1{\rm{M}})\mid {\rm{Cu}}\)
2. Oxidation half-reaction is represented as \({\rm{Zn}}\mid {\rm{Z}}{{\rm{n}}^{2 + }}(0.1{\rm{M}})\)
3. Salt bridge is represented as \(||\)
4. The anode is always written on LHS and cathode on RHS.
5. Thus the Electrochemical cell can be represented as \({\rm{Zn}}\left| {{\rm{Z}}{{\rm{n}}^{2 + }}\left. {\left( {0.1\,{\rm{M}}} \right)} \right\|{\rm{C}}{{\rm{u}}^{2 + }}(0.1{\rm{M}})} \right|{\rm{Cu}}\)

Applications of Electrochemical Cell

1. In metallurgy, electrolytic cells are used in the electrorefining of many non-ferrous metals, producing highly pure metals such as lead, zinc, aluminium, and copper. Electrolytic cells are used in the electrowinning of these metals.
2. It is used to extract pure sodium metal from molten sodium chloride by keeping it in an electrolytic cell.
3. Electrochemical cells convert chemical energy into electrical energy. This process is used in the daily use batteries that are of two types:
   (i) Primary cells – These cells are of use and throw types of batteries. They are non-rechargeable and irreversible, used in remotes and torches. The electrochemical reactions are irreversible.
   (ii) Secondary cells – The cells are rechargeable and reversible, i.e., they can function as both galvanic and electrolytic cells. The most widely used battery is a Lithium-ion battery used in automobiles and electronic gadgets.
4. Silver oxide batteries are used in hearing aids devices.
5. Thermal batteries are used for military purposes, such as in Navy devices.
6. Fuel cells work on conventional combustion-based technologies and have a wide range of applications in transportation, material handling, stationary, power backup applications, and power plants.

Summary

An electrochemical cell is a device that may either create electrical energy from chemical processes taking place inside it or use electrical energy given to it to help chemical reactions take place inside it. Chemical energy may be converted to electrical energy or vice versa using these technologies. A conventional 1.5-volt cell, which is used to power numerous electrical items such as TV remotes and clocks, is an example of an electrochemical cell.

Thus we can conclude that Electrochemistry is the branch of chemistry that establishes the relation between chemical energy and electrical energy. The key feature of an electrochemical cell is the redox reaction which takes place in an electrolytic solution at the interface of the conductors. Based on the types of redox reactions going inside, electrochemical cells are divided into two types: Galvanic cell or voltaic cell and Electrolytic cell. A voltaic cell or galvanic cell comprises two half cells composed of metal electrodes like copper and zinc.

These electrodes behave as cathode and anode. A salt bridge is made using a U-shaped tube filled with saline solution to connect the two half cells. Electrochemical cells convert chemical energy into electrical energy and vice-versa. In contrast, electrolytic cells convert electrical energy into chemical energy through electrolysis. We use these electrochemical cells in batteries in various applications such as remotes, laptops, mobile phones, and many other electronic gadgets. Though they are beneficial to us, they may add to soil pollution by solid wastes. Some electrochemical cells are not reusable and can leak toxic chemicals and acids. Thus we should promote using rechargeable batteries in our daily life.

FAQs on Electrochemical Cells

Q1: What is an electrochemical cell, and how does it work?
A1: An electrochemical cell is an apparatus or device that produces electric current from chemical change and energy released by this spontaneous redox reaction. During this chemical reaction, electrons are transferred from one chemical species to another, producing an electric current.

Q2: What are the two types of electrochemical cells?
A2: Based on the reactions going inside, electrochemical cells are divided into two types: Galvanic cell or voltaic cell and Electrolytic cell. Galvanic cells convert chemical energy into electrical energy, and electrolytic cells convert electrical energy into chemical energy.

Q3: What is the principle of an electrochemical cell?
A3: The basic principle of working of an electrochemical cell is the transfer of electrons generated from a redox reaction occurring in it that results in the production of electric current.

Q4: What is the function of an electrochemical cell?
A4: The function of an electrochemical cell is to convert chemical energy to electrical energy from the chemical reactions going in it or to convert electrical energy to chemical energy.

Q5: What is an electrochemical cell? Explain with an example?
A5: The device that brings about electrical energy from the chemical reactions going in it or uses chemical energy to produce electricity is known as an electrochemical cell. One of the most common examples of an electrochemical cell (galvanic cell) used in our daily life is a \(1.5\;{\rm{V}}\) cell.

Q6: What are some of the applications of electrochemical cells?
A6: Electrochemical cells find applications in torches, military applications, corrosion protection, digital watches, etc.

Q7: What are the advantages and disadvantages of electrochemical cells?
A7: The advantages of electrical cells are innumerable. They are used in electrolytic refining of metals, electroplating, and batteries. Batteries of different types are used in various applications such as automobiles, and electronic gadgets like laptops, mobile phones, and tablets. Galvanic cells have a disadvantage as they cannot be used again once the chemical reactions inside them reach equilibrium. As we throw them after use, this leads to soil pollution by solid wastes. Some electrochemical cells are not reusable and can leak toxic chemicals and acids.

Q8: What are the four components of an electrochemical cell?
A8: The four components of an electrochemical cell are Anode – The cell compartment where oxidation takes place. Cathode – The cell compartment where reduction takes place. Electrolyte – An electrolyte is a compound that produces ions resulting in an electrically conducting solution when dissolved in polar solvents, such as water and salt bridge that connects the oxidation half and reduction half of an electrochemical cell and completes the electrochemical circuit. It is filled with a saturated salt solution like \({\rm{KCl }}\).

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