Electrochemical Cell

Introduction

An electrochemical cell is a system that can generate electrical energy from spontaneous chemical reactions. Lets discuss it further,

How does the battery in a mobile phone charge when it is plugged into its charger or how does the cell in a TV remote control function? In the scientific field known as electrochemistry, all these queries have their answers. The study of electrochemistry includes both the use of electricity to conduct non-spontaneous chemical reactions as well as the production of electricity through chemical reactions. Cells are employed to attain the goal. Cells are components that cause chemical reactions that result in electricity or generate electricity.

What is an electrochemical reaction?

Any process that is either brought on or accompanied by the flow of electrical current and typically involves the electron transport among two substances-one a solid and another a liquid-is considered an electrochemical reaction. A solid electrode and a material, like an electrolyte, interact with each other to undergo an electrochemical reaction. By producing an electric current to pass across the electrodes, this flow causes the reaction to release or absorb heat. The oxidation no. of all the atoms involved in the reaction change when, for instance, two electrodes in contact with one another trigger an oxidation and reduction (redox) reaction.

The process of electrochemical reaction

The properties of the negatively charged e- determine how matter interacts with an electric current as it flows through a system. Since protons are positively charged units of matter that can be found in elements, groups of atoms, or molecules, the electron, the fundamental unit of electricity, has a strong attraction to them.

The chemical attraction that particles have for one another is comparable to this attraction. Every chemical reaction causes an alteration in the structure of an atom's electrons, and these liberated electrons can either unite with particles of matter to form reductions or be ejected by them (oxidation). The rules of Faraday specify the quantitative link between the free e- in a current flow and the atoms of a substance wherein they trigger a reaction. The components of electrochemical processes, often known as ionic conductors or electrolytes

What is an electrochemical cell?

A system that can generate electrical energy from spontaneous chemical reactions is an electrochemical cell. Redox reactions are the chemical processes that take place throughout this process. Electrons are transferred between chemical species during redox reactions. They are also named Galvanic or voltaic cells. The Daniell cell is an example of an electrochemical cell.

An electrochemical cell's essential parts are −

• An electrolyte- is a substance found between the electrodes that, when dissolved in polar solvents like water, creates freely flowing ions that result in an electrically conducting solution.

• Electrodes- are the solid electrical conductors used in electrochemical cells made of good conductors like metals.

They come in two varieties −

• The Cathode - The area of the cell where reduction occurs.

• The anode- is the area of the cell where oxidation occurs.

• Salt bridge- An electrochemical cell's oxidation and reduction halves are connected by a salt bridge, completing the circuit. It is stuffed full of 𝐾𝐶𝑙− and other saturated salt solutions. The bridge is necessary for the solution's ions to flow between half-cells, which is required.

What are the types of electrochemical cells?

There are two main types −

• Galvanic Cell / Voltaic Cell − In these electrochemical cells, chemical energy is converted to electrical energy.

• Electrolytic Cell − In these cells, electrical energy is converted to chemical energy.

Explain the working:

Working Principle

The fundamental operating principle of an electrochemical system is the transfer of e- produced by a redox reaction taking place in it, which produces an electric current.

Working mechanism:

When the switch is turned on after an electrochemical cell has been fully assembled, a deflection is seen in the galvanometer of the external circuit. The galvanometer's needle moves in the direction of the beaker carrying the copper sulphate solution. It shows that the current has moved from the copper sulphate solution beaker to the zinc sulphate solution beaker. When the circuit is finished, a change takes place that results in the oxidation of zinc atoms in the zinc electrode and the reduction of Cu atoms in the copper rod. Two electrons are released by zinc, and through an external circuit, copper accepts them.

$$\mathrm{Full\:redox\:reaction\::\:Zn(s)\:Cu^{2+}(aq)\:\rightarrow\:Zn^{2+}(aq)\:+\:Cu(s)}$$

How do you calculate electrochemical cell potential?

The reaction's electrochemical cell potential is often referred to as the cell's standard emf. Based on a process that can be divided into two half-reactions, reduction half- reaction, and oxidation half-reaction, the electrochemical cell is created.

• Reduction of half-reaction − by gaining electrons metal is formed.

• Oxidation half-reaction − cations are formed by the loss of electrons.

Let us examine the zinc and copper example −

$$\mathrm{Zn(s)\:Cu^{2+}(aq)\:\rightarrow\:Zn^{2+}(aq)\:+\:Cu(s)}$$

These copper ions change into copper metal near the cathode, where they are then further deposited. The formula is

$$\mathrm{Cu^{2+}\:+\:2e^{-}\:\rightarrow\:Cu(s)}$$

Cell representation will be like −

$$\mathrm{Zn\:\lvert\:Zn^{2+}(aq)\:\rvert\:\:\lvert\:Cu^{2+}(aq)\:\rvert\:Cu}$$

The cathode and anode of the cell, respectively, will be on their right and left sides.

The difference between both the standard EMFs of the cathode and the anode constitutes the standard emf of the electrochemical reaction's cell.

The formula appears as follows −

$$\mathrm{E^{0}_{cell}\:=\:E^{0}_{cathode}\:-\:E^{0}_{anode}}$$

If normal circumstances are not there for reaction to occur, the following formula can be applied −

$$\mathrm{E_{cell}\:=\:E^{0}_{cell}\:-\:\frac{RT}{nF}lnQ}$$

Where n stands for the number of electrons involved in the process, T stands for temperature, F stands for Faraday's number, and Q stands for reaction quotient.

Application of electrochemical cell:

• Many non-ferrous metals are electro-refined in metallurgy using electrolytic cells, which results in the production of very pure metals like 𝑃𝑏, 𝑍𝑛, 𝐴𝑙, and 𝐶𝑢. These metals are electrowon using electrolytic cells.

• By storing it in an electrolytic cell, it is utilised to recover pure 𝑁𝑎 metal from molten 𝑁𝑎𝐶𝑙.

• In hearing aids, silver oxide batteries are used.

• In Navy gadgets, thermal batteries are employed for military applications.

Example of electrochemical reaction

Whenever aqueous solutions are utilised. The most straightforward redox reaction for it is as follows −

• In the cathode − $\mathrm{2H_{2}O\:+\:2e^{-}\:\rightarrow\:H_{2}\:+\:2OH^{-}\:(Water\:is\:reduced)}$

• In the anode − $\mathrm{2H_{2}O\:\rightarrow\:4H^{+}\:+\:O_{2}\:+\:4e^{-}(Water\:is\:oxidised)}$

When an active metal is a cation being used, $\mathrm{H_{2}O}$ is reduced at the cathode. Whenever the anion is a polyatomic ion in the anode, water is oxidised.

Corrosion is an additional fantastic illustration of an electrochemical process. When bare iron is in touch with moisture, it rusts rapidly due to an electrochemical reaction in which a droplet of water transforms into a tiny galvanic cell (it oxidises the iron).

Electrochemistry application

• Electrical batteries are created using the concepts of cells. A battery is a device used in science and technology that saves chemical energy and provides access in electrical form.

• Defence applications (thermal batteries)

• Electronic cameras (Li batteries)

• Audio devices (silver-oxide batteries)

• Electroplating serves a variety of purposes, including the manufacturing of jewellery and the protection of some metals from corrosion.

• Electrochemistry is required in several sectors, including the chlor alkali business.

Conclusion

The study of electrochemistry is fascinating. Electrochemical reactions are important to understand because they have enormous academic and practical relevance. Understanding the replies helps us to comprehend how everyday objects like a battery or cell work. Chemical energy created by chemical processes can be used to produce electrical energy in electrochemical cells, and chemical energy can be produced using electrical energy.

FAQs

1. What distinguishes the Daniell cell from a voltaic cell?

Depending on the current provided or drawn, a voltaic cell may or not be reversible, whereas the Daniell cell always is.

2. What factors affect electrode potential?

The ability of an electrode to take electrons is known as the reduction potential, while oxidation potential refers to the tendency of an electrode to lose electrons. The temperature and metal ion concentration at an electrode's surface determine its potential.

3. From Delta G, how do you determine standard cell potential?

In a galvanic cell, the Gibbs free energy is connected to the potential by the formula $\mathrm{G^{0}cell\:=\:nFE^{0}cell}$The reaction can happen if E°cell > 0.

4. Can you use a zinc pot to hold copper sulphate solution?

Copper is less reactive than zinc. Zinc can therefore remove 𝐶𝑢 from its salt solution. If the $\mathrm{CuSO_{4}}$ ,The solution is kept in a zinc container, copper will be removed from the solution.

$$\mathrm{Zn\:+\:CuSO_{4}\:\rightarrow\:ZnSO_{4}\:+\:Cu}$$

Therefore, a zinc pot cannot be used to store the copper sulphate solution.

5. What is the emf measurement in the SI system?

The energy contained in a battery per Coulomb of charge is known as the electromotive force, EMF has a SI unit of volts, which is equal to joules per coulomb.