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PRESENTER MS FARZANA MEHBOOB Head of the Science department

PRESENTER MS FARZANA MEHBOOB Head of the Science department. D.A.Neelum high school. INSTRUCTIONAL LESSON ELECTROLYSIS. TOPIC: Electrolysis & its Application. Division of lesson. Qualitative Aspect of Electrolysis Quantitative Aspect of Electrolysis.

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PRESENTER MS FARZANA MEHBOOB Head of the Science department

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  1. PRESENTER MS FARZANA MEHBOOBHead of the Science department D.A.Neelum high school

  2. INSTRUCTIONAL LESSON ELECTROLYSIS

  3. TOPIC: Electrolysis & its Application

  4. Division of lesson • Qualitative Aspect of Electrolysis • Quantitative Aspect of Electrolysis

  5. LEARNING OBJECTIVES(Low order thinking) • What is electrolysis? • Terminologies use in electrolysis • Differences between a galvanic cell and electrolytic cell • Electrolysis mechanism • The equations of the reactions take place at electrodes • The various applications of electrolysis with examples

  6. BLOOM BASED OBJECTIVES (Highorder thinking) • Use a Venn diagram to show how electrolytic cell and electrochemical cell are similar and different. ANALYSING • Conduct an experiment to check whether sodium chloride can act as an electrolyte in solid state or can not. Give reason.

  7. BLOOM BASED OBJECTIVES(Highorder thinking) • Form a panel to discuss the influence of electrolysis on our lives. EVALUATING • State one advantage of Down process from a pollution point of view and also one commercial advantage.

  8. BLOOM BASED OBJECTIVES(Highorder thinking) • Suggest how could the experiment be changed to avoid the formation of poisonous fumes of chlorine gas in the given experiment. CREATING • Investigate what economic and environmental issues might influence the siting of the purification plant during the purification of copper on the large scale. Make a PPt presentation..

  9. Electrolysis Humphry Davy 1778-1829. Prepared metallic K, Na, Sr, Ca, B, Ba, Mg, Li by electrolysis.

  10. WHAT IS ELECTROLYSIS

  11. DEFINITION Electrolysis is the passage of an electric current through resulting A Polar compound that is either molten or dissolved in a suitable solvent, • in chemical reactions at the electrodes and separation of materials.

  12. GENERAL TERMS USED IN ELECTROLYSIS Electrolytic cell It has three component parts: • An electrolyte • Two electrodes (a cathode and an anode). • A battery

  13. ELECTROLYTES • substance that conducts electric current a result of a dissociation into positively and negatively ions in solution or molten form. • Examples: • Molten salts • Solution of salts in water • Solution of acids • Solutions of alkalis

  14. TYPES OF ELECTROLYTE

  15. Electrode • In an electrolytic cell: • Anode is a Positive electrode • Cathode is a negative electrode REMEMBER the story?

  16. An OxRed Cat Anode Oxidation Story of & Reduction Cathode

  17. Positive • Anode • Negative • Is • Cathode Don’t get stressed in the exam: Remember PANIC

  18. Some key differences with an electrochemical cell set-up: • No salt bridge • An electrochemical cell will be required • Anode is POSITIVE electrode • Cathode is NEGATIVE electrode

  19. WHAT HAPPENS IN ELECTROLYSIS BATTERY (Electron pump) Electrons move back to battery to complete the circuit Electron flow Negatively charged ion Positively charged ion Give up electrons to the electrode Electron leave the electrode Ions discharged as atom Ions discharged as atom Anode(+) Cathode(-) Electrolyte

  20. WHAT HAPPENS IN ELECTROLYSIS BATTERY (Electron pump) Electrons move back to battery to complete the circuit Electron flow + _ + _ _ + Anode(+) Cathode(-) Electolyte

  21. Think of electrolysis and electrolytic cells as the opposite of electrochemical cells:

  22. Chemical → Electrical Electrical → chemical Yes No Positive Negative recharging batteries & electroplating batteries

  23. IN THE PROCESS OF ELECTROLYSIS • Conduction of Electricity • Supplying of energy • Carrying of electric current • Note: • Electrons do not actually pass through the liquid.

  24. PROCESS OF ELECTROLYSIS • Movement of ions • Cations = Cathode • Anions = Anode • Discharge of ions AT CATHODE ALWAYS PRODUCE METAL OR HYDROGEN

  25. EXAMPLE • ELECTROLYSIS OF MOLTEN NaCl 2NaCl(s)→ 2Na+ (l)+Cl-(l)

  26. Sodium metal at the (-)Cathode 2Na+  +  2e-→   2Na Chlorine gas at the (+)Anode 2Cl-  -  2e-→  Cl2 • The overall reaction is 2Na+Cl-(l)→   2Na(s)  +   Cl2(g)

  27. Electrolysis of Molten NaCl - + CATHODE ANODE The metal goes to the cathode and the non metal goes to the anode. - + Na+ Cl- Cl- Cl- Na+ Na+ Na+ Cl-

  28. Activity

  29. Match up the words with their descriptions Positive electrode Electrolyte The substance being broken down Anode Splitting a substance using electricity Cathode Negative electrode Anion Positive ion Cation Negative ion Electrolysis

  30. VIDEO OF ELECTROLYSIS

  31. Factors affecting the SELECTIVE discharge of ions SELECTIVE discharge of ions? FACTORS:- 1.Relative positions of the ion in the metal activity series. 2. The concentration of ions in the electrolyte 3. The nature of electrode

  32. 1-RELATIVE POSITIONS OF THE ION IN THE METAL ACTIVITY SERIES.

  33. FACTORS (Contd) 2. The concentration of ions in the electrolyte • Higher the concentration of ions in the electrolyte ……………..? 3. The nature of electrode • Inert electrodes : iron, carbon, platinium • Active electrodes : copper, nickel

  34. PREDICTING WHAT WILL BE FORMED IN AN ELECTROLYSIS Sodium Bromine Iodine Potassium Fluorine Calcium Oxygen Magnesium Chlorine Lithium

  35. Industrial Application of electrolysis

  36. Extraction processes The reactivity of a metal determines the method of extraction. The Reactivity Series potassium Increasing reactivity sodium Metals above carbon must be extracted using electrolysis. calcium magnesium aluminium (carbon) zinc Metals below carbon can be extracted from the ore by reduction using carbon, coke, or charcoal. iron lead copper silver Gold and silver often do not need to be extracted. They occur native. gold

  37. 1- EXTRACTION OF METALSEXAMPLE = ALUMINIUM METAL) Electrolysis of molten Alumina • The electrolyte a solution of alumina in cryolite melts at about 900 °Cand electrolysis is done at about 950 °C. • Electrolysis separates the molten ionic compound into its elements.

  38. Electrolysis of molten Alumina

  39. REACTIONS • Aluminium metal at the (-)cathode 4Al3+  +  12e- → 4Al  (Reduction) • Oxygen gas at the (+)anode 6O2-→ 3O2 + 12e- (Oxidation) The overall reaction 2Al2O3(l) →      4Al(l)   +     3O2(g)

  40. 2-PREPARATION OF ALKALI & CHLORINE GAS • The NaCl will split into Na+ and Cl - ions • Water splits into H + and OH - ions. Qs? • What will happen during electrolysis?

  41. 2-PREPARATION OF ALKALI & CHLORINE GAS

  42. REACTIONS • At the Cathode 2H+  +  2e- → H2 • At the Anode 2Cl– → Cl2 + 2e- The overall reaction • 2NaCl + 2H2O → Cl2 + H2 + 2NaOH

  43. NELSON CELL

  44. 3- ELECTROPLATING • PURPOSE? • Most commonly used metals for electroplating • Copper, Chromium, Silver, Tin

  45. Gold plating external power source external power source Au Au Au+(aq) Au+(aq) cathode: Au+(aq) +e-→Au anode: Au→Au+(aq) +e-

  46. 4-ELECTRO REFINING OF METALS • is a process by which metals containing impurities are purified by electrolysis to give a pure metal. • EXAMPLE:- ELECTRO REFFINING OF COPPER

  47. ELECTRO REFINING OF COPPER

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