Unit_I_Electrochemistry.ppt
- 1. DEPARTMENT OF CHEMISTRY WELCOMES YOUALL 22CYT28-Chemistry for Information Technology 2022R Prepared By Krishnaveni K Assistant Professor Department of Chemistry Kongu Engineering College, Perundurai, Erode
- 2. Introduction – cells – types - representation of galvanic cell - electrode potential - Nernst equation (derivation of cell EMF) - calculation of cell EMF from single electrode potential - reference electrode: construction, working and applications of standard hydrogen electrode, standard calomel electrode - glass electrode – EMF series and its applications - potentiometric titrations (redox) - conductometric titrations - mixture of weak and strong acid vs strong base. UNIT-II ELECTROCHEMISTRY
- 3. ELECTROCHEMISTRY INTRODUCTION It is a branch of chemistry The study of process involved in the interconversion of chemical and electrical energy. KEY TERMS IN ELECTROCHEMISTRY Conductor: Material which conduct electric current Non conductor: Material which do not conduct electric current Current: The flow of electrons through a wire or any conductor Oxidation: Loss of electrons Reduction: Gain of electrons Redox reaction: oxidation and reduction reactions occur simultaneously Reducing agent: A reactant in which donates an electron to the reduced species. (The reducing agent is oxidized) 5-Jul-23
- 4. Oxidizing agent: A reactant in which accepts an electron from the oxidized species. (The oxidizing agent is reduced) Anode: The electrode at which oxidation occurs Cathode: The electrode at which reduction occurs Electrolyte: A water soluble substance and conduct an electric current Half cell: A single electrode immersed in an electrolytic solution and developing a definite potential difference. Cell: Two half cells are connected through one wire Oxidation Potential : It is the tendency of an electrode to loss electrons Reduction potential: It is the tendency of an electrode to gain electrons Electrode Potential: It is the tendency of an electrode to loss or gain electrons Single Electrode Potential: It is the tendency of an electrode to loss or gain electrons when it is dipped in its own salt solution. (Standard- 1M concentration at 250C). 5-Jul-23
- 7. Reference electrode The electrode of standard potential with which we can compare the potentials of other electrode is called a reference electrode. It can acts both as anode or cathode depending upon the nature of other electrode. Classification: i) Primary reference electrodes Ex : Standard Hydrogen Electrode (SHE) ii) Secondary reference electrodes Ex: Calomel, Ag/AgCl electrodes and Quinehydrone electrodes v Reference Electrode Working or Indicator Electrode The part of the cell that is kept constant The part of the cell that contains the unknown solution
- 8. Construction and Working of Standard Calomel Electrode (SCE) A common reference electrode. It consists of a wide glass tube. Mercury is placed at the bottom of the glass tube. A paste of mercury and mercurous chloride(Calomel) is placed above the mercury. The remaining portion above the paste is filled with a KCl solution of known concentration (0.1N, 1.0N and saturated) . A platinum wire is immersed into the mercury to obtain electrical contact. The side arm is provided for making electrical contact through a salt bridge. Pt wire
- 9. Electrode representation: Hg, Hg2Cl2(s)// KCl(satd. solution) Working of the electrode: If it acts as Cathode : Hg2Cl2 Hg2 2+ +2Cl- Hg2 2+ +2e- 2Hg Hg2Cl2+2e- 2Hg+2Cl- if it acts as anode : 2Hg Hg2 2+ +2e- Hg2 2+ +2Cl- 2Hg+2Cl- Hg2Cl2+2e- Hg2Cl2 KCl E in Volts saturated 0.2422V 1.0N 0.2800 V 0.1N 0.3338V Electrode potential
- 10. Measurement of pH using Calomel electrode
- 11. Measurement of pH using Calomel electrode Hydrogen electrode containing a solution of unknown pH combine with the calomel electrode to set up a complete cell. We use a saturated calomel electrode as the reference and the complete cell can be represented as : Pt, H2 (1atm)/ H+ (C=?)/ /KCl(satd. solution)/Hg2Cl2(s), Hg
- 13. Merits It is easy to construct and easy to transport. It provides almost a constant potential value with varying temperature and finds application in laboratories for measuring potential of an electrode. It is used in corrosion studies.
- 14. REFERENCES: 1.Palanisamy P.N., Manikandan P., Geetha A.& Manjula Rani K, “Applied Chemistry”, 6th Edition, Tata McGraw Hill Education Private Limited, New Delhi, 2019. 2 .Paya Payal B.Joshi, Shashank Deep., “Engineering Chemistry”, Oxford University Press, New Delhi, 2019. 3.Palanna O., “Engineering Chemistry”, McGraw Hill Education, New Delhi, 2017. 5-Jul-23