Electro chemical cells

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  • In voltaic cells, the redox reaction is spontaneous, so it doesn’t require an outside energy source.
  • Electro chemical cells

    1. 1. PRESENTATION OF CHEMISTRY
    2. 2. PRESENTED TOMA’AM TAHIRA TARIQ PRESENTED BY HINA JABEEN ROLL NO: 120
    3. 3. TEACHING MATERIALS White board Duster Marker Books
    4. 4. GENERAL OBJECTIVES Enable the student to acquire comprehension of chemistry. To compare learnt knowledge with surrounding. To develop interest among student towards chemistry. Enable the student to apply the leant knowledge.
    5. 5. SPEACIFIC KNOWLEDGEAt the end of the topic student will be able to Sketch a Denial cell, label cathode, anode and direction of the flow of electron. Distinguish between electrolytic and voltaic cell. Identify half cell in which oxidation occur and half cell in which reduction occur in voltaic cell.
    6. 6. Previous knowledge Define electro chemical cell? What are the types of electro chemical cell, name them? Define electrolytic cell and voltaic cell?
    7. 7. INTRODUCTION ELECTRO CHEMICAL CELL: An arrangement which consist of electrodes dipped into an electrolyte in which chemical reaction uses/generates electric current . ELECROLYTIC CELL: The electro chemical cell in which a reaction occur with the help of electric current. VOLTAIC/GALVANIC CELL: The electro chemical cell in which a reaction generates electric current.
    8. 8. ELECTRO-CHEMICAL REACTIONWe discuss electrolysis of :A) fused saltB) Aqueous solution of salt
    9. 9. Electrolysis of aq. sol. of Salt  Not so simple  Reason Undergoes REDOX reaction of H2O•Along with redox reaction of dissolved salt•Product -------not precisely predicted e.g. KNO3
    10. 10. Electrolysis of aq. Sol of KNO3 It dissociate as: KNO3 K+ + NO3-H2O + H2O H3O+ + OH-
    11. 11. Aqueous KNO3 - battery + power source e- e- KNO3 (aq) What could be reduced at the cathode? K+ NO3- (-) (+) cathode H2O anode different - half-cell
    12. 12. Reaction at cathode from+K KNO3 Not discharge At cathodeReason Small concentration H3O +& OH- Formed By Dissociation of H2O
    13. 13. H3O + takes e- from cathode Formed Hº Hº Hº Combine H2 At Cathode
    14. 14. Reaction at anodeNO3 - Tendency AnodeOH- To move - Oxidation of OH - Easier than NO3 OH - discharge O2 + H2O
    15. 15. RESULT - K+ & NO3 remain in solution Water is electrolyzed and converted into H2 and O2 H2O is electrolyzed in presence of KNO3
    16. 16. Voltaic Cells Invented by Alessandro Volta in 1800 Voltaic cells: electrochemical cells used to convert chemical energy into electrical energy  Examples  flashlights or battery- powered calculators  Made of half cells  One part of the voltaic cell where oxidation or reduction is occurring
    17. 17. VOLTAIC CELL/GALVANIC CELL:To understand the working of voltaic cell, take example of Daniel cell
    18. 18. GALVANIC CELL/ VOLTAIC CEL TWO HALF CELLSLEFT HALF CELL RIGHT HALF CELL CONNECTED THROUGH SLT BRIDGE
    19. 19. LEFT HALF CELL CONTAINS Zn METAL STRIP DIPPED INGiving equilibrium 1M ZnSO4 ANODE
    20. 20. RIGHT HALF CELL CONTAINS COPPER METAL STRIP DIPPED INGiving equilibrium 1M Cu SO4 CATHODE
    21. 21. CellConstruction Cu Zn 1.0 M CuSO4 1.0 M ZnSO4
    22. 22. leave Zn electrode e - Cu electrode Zn CuGIVING NET GIVING NET+ive CHARGE -ive CHARGE Electron flow from External circuit Zn electrode Cu electrode
    23. 23. Working of galvanic cell
    24. 24. REDOX REACTION REDOXLEFT HALF CELL REACTION REACTION OR VOLTIC CELLRIGHT HALF CELL REACTION REACTION
    25. 25. Galvanic cell cathode half-cell REDUCTION Cu+2 + 2e-  Cu anode half-cell OXIDATION Zn  Zn+2 +2e- overall cell reaction Zn + Cu+2  Zn+2 + Cu Spontaneous reaction that produces electrical current!
    26. 26. What about half-cell What about the sign of reactions? the electrodes? + - Why? cathode half-cell anode half-cellCu+2 + 2e-  Cu Zn  Zn+2 + 2e- Cu Zn plates out What electrode or happened erodes deposits Cu at each Zn or dissolves on electrode? electrode 1.0 M CuSO4 1.0 M ZnSO4
    27. 27. flow1.1V current Zn electrode from to through External circuit Cu electrode Reduction Cu electrode having Oxidation Zn electrode concentration 1 M solution each Temperature = 25˚c
    28. 28. Now replace the light bulb with a volt meter. + 1.1 volts - cathode half-cell anode half-cellCu+2 + 2e-  Cu Zn  Zn+2 + 2e- Cu Zn 1.0 M CuSO4 1.0 M ZnSO4
    29. 29. SALT BRIDGEStrong Electrolyte KCL, KNO3, K2SO4 Saturated Solution of Porous Ends at both sides Sealed Glass / Wool / Cotton Plug
    30. 30. Comparison of Electrochemical Cells Galvanic Electrolytic Produces electrical current Need power source Non spontaneous Spontaneous redox reaction redox reaction Electric condition Electrolysis take place take place
    31. 31. QUESTIONS
    32. 32. FILL IN THE BLANKS ____________of aq. Sol. of salt is not so simple Electrolysis of aq. Sol. of _____is not so simple KNO3 < >______ +NO ¯ 3 _______< > K+ +NO ¯ 3 H O +e< 2 > Hº + ______
    33. 33.  Two _______atom combine to form hydrogen gas Hydrogen gas is formed by the combination of two ________ atoms. OH¯ OHº + e 4OH- O2 +_________ In electrolysis of water, H2O is converted into_____ and _____ _______ is used as electrolyte in electrolysis of H2O _______ cell is an example of voltaic cell
    34. 34. 1. Voltaic/galvanic cell consist of _____ half cell2. Two half cell are connected through ___________3. Right half cell contain _____ metal strip4. Left half cell contain _____ metal strip5. Cu metal strip is dipped into 1M sol. Of ______6. Zn metal strip is dipped into 1M sol. Of ______7. Sum of two half cell reaction is called ________ reaction
    35. 35. 1. Salt bridge is _____ shape2. Salt bridge is made up of ______ tube3. Tube of salt bridge is ______ at both end4. End of salt bridge Is made up of _____ material5. _______ material hold the solution in U shaped
    36. 36. Identify the following Anode Cathode + 1.1 volts - Salt bridge Cu Zn

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