5Division of lessonQualitative Aspect of ElectrolysisQuantitative Aspect of Electrolysis
6LEARNING OBJECTIVES (Low order thinking) What is electrolysis?Terminologies use in electrolysisDifferences between a galvanic cell and electrolytic cellElectrolysis mechanismThe equations of the reactions take place at electrodesThe various applications of electrolysis with examples
7BLOOM BASED OBJECTIVES (Highorder thinking)Use a Venn diagram to show how electrolytic cell and electrochemical cell are similar and different.ANALYSINGConduct an experiment to check whether sodium chloride can act as an electrolyte in solid state or can not. Give reason.
8BLOOM BASED OBJECTIVES (Highorder thinking) Form a panel to discuss the influence of electrolysis on our lives.EVALUATINGState one advantage of Down process from a pollution point of view and also one commercial advantage.
9BLOOM 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.CREATINGInvestigate 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..
10Electrolysis Humphry Davy 1778-1829. Prepared metallic K, Na, Sr, Ca, B, Ba, Mg, Li by electrolysis.1111
11electricity Break apart Electrolysis Electro lysis WHAT IS ELECTROLYSISElectrolysisLatin wordElectroelectricityandlysisBreak apartthrough
12in chemical reactions at the electrodes and separation of materials. through resultingDEFINITIONElectrolysis is the passage of an electric currentA Polar compound that is either molten or dissolved in a suitable solvent,in chemical reactions at the electrodes and separation of materials.
13GENERAL TERMS USED IN ELECTROLYSIS Electrolytic cellIt has three component parts:An electrolyteTwo electrodes (a cathode and an anode).A battery
14ELECTROLYTESsubstance that conducts electric current a result of a dissociation into positively and negatively ions in solution or molten form.Examples:Molten saltsSolution of salts in waterSolution of acidsSolutions of alkalis
16ELECTRICAL CONDUCTIVITY Metallic conductivity Electron flow Is of two typesMetallic conductivityElectron flowA property of elementTake place in solid &liquidNo chemical change occurElectrolytic conductivityIons flowA property of polar compoundsTake place in liquid & solutionChemical change occur
17In an electrolytic cell: Anode is a Positive electrode Cathode is a negative electrodeREMEMBERthe story?
18Anode OxidationStory ofAn Ox Red Cat&Reduction Cathode
19Positive Anode Negative Is Cathode Don’t get stressed in the exam: Remember PANIC
20Some key differences with an electrochemical cell set-up: No salt bridgeAn electrochemical cell will be requiredAnode is POSITIVE electrodeCathode is NEGATIVE electrode
21WHAT HAPPENS IN ELECTROLYSIS BATTERY(Electron pump)Electrons move backto battery to completethe circuitElectron flowNegatively chargedionPositivelychargedionGive up electrons to theelectrodeElectron leavethe electrodeIons discharged as atomIonsdischarged as atomAnode(+)Cathode(-)Electrolyte
22WHAT HAPPENS IN ELECTROLYSIS BATTERY(Electron pump)Electrons move backto battery to completethe circuitElectron flow+_+__+Anode(+)Cathode(-)Electolyte
23Think of electrolysis and electrolytic cells as the opposite of electrochemical cells:
24Chemical → Electrical Electrical → chemical Yes No Electrochemical CellsElectrolyticCellsEnergy conversionSpontaneous chemicalreaction?Value of E°ExamplesChemical → ElectricalElectrical → chemicalYesNoPositiveNegativerecharging batteries & electroplatingbatteries
25IN THE PROCESS OF ELECTROLYSIS Conduction of ElectricitySupplying of energyCarrying of electric currentNote:Electrons do not actually pass through the liquid.
26PROCESS OF ELECTROLYSIS Movement of ionsCations = CathodeAnions = AnodeDischarge of ionsALWAYS PRODUCEAT CATHODEMETAL OR HYDROGEN
27ELECTROLYSIS OF MOLTEN NaCl 2NaCl(s) → 2Na+ (l) + Cl-(l) EXAMPLEELECTROLYSIS OF MOLTEN NaCl2NaCl(s) → 2Na+ (l) + Cl-(l)
28Sodium metal at the (-)Cathode 2Na+ + 2e- → 2NaChlorine gas at the (+)Anode2Cl- - 2e- → Cl2The overall reaction is2Na+Cl-(l) → 2Na(s) + Cl2(g)
29Electrolysis of Molten NaCl -+ANODECATHODEThe metal goes to the cathode and the non metal goes to the anode.-+Na+Cl-Cl-Cl-Na+Na+Na+Cl-
31Splitting a substance using electricity Match up the words with their descriptionsPositive electrodeElectrolyteThe substance being broken downAnodeSplitting a substance using electricityCathodeNegative electrodeAnionPositive ionCationNegative ionElectrolysis
33Factors 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
341-RELATIVE POSITIONS OF THE ION IN THE METAL ACTIVITY SERIES.
352. The concentration of ions in the electrolyte FACTORS (Contd)2. The concentration of ions in the electrolyteHigher the concentration of ions in the electrolyte ……………..?3. The nature of electrodeInert electrodes : iron, carbon, platiniumActive electrodes : copper, nickel
36PREDICTING WHAT WILL BE FORMED IN AN ELECTROLYSIS CompoundAnodeCathodeSodium BromidePotassium IodideCalcium FluorideMagnesium OxideLithium ChlorideBromineSodiumIodinePotassiumFluorineCalciumOxygenMagnesiumChlorineLithium
37PREPARATION OF ALKALI & CHLORINE GAS ELECTROPLATINGEXTRACTION OF METALSANODIZINGELCTROREFININGPREPARATION OF ALKALI & CHLORINE GASIndustrialApplication of electrolysis
38Increasing reactivity Extraction processesThe reactivity of a metal determines the method of extraction.The ReactivitySeriespotassiumIncreasing reactivitysodiumMetals above carbon must be extracted using electrolysis.calciummagnesiumaluminium(carbon)zincMetals below carboncan be extracted from the ore by reduction using carbon, coke, or charcoal.ironleadcoppersilverGold and silver often do not need tobe extracted. They occur native.gold
391- EXTRACTION OF METALS EXAMPLE = ALUMINIUM METAL) Electrolysis of molten AluminaThe electrolyte a solution of alumina in cryolite melts at about 900 °C and electrolysis is done at about 950 °C.Electrolysis separates the molten ionic compound into its elements.
463- ELECTROPLATING PURPOSE? Most commonly used metals for electroplatingCopper, Chromium, Silver, Tin
47Gold plating cathode: Au+(aq) +e-→Au anode: Au→Au+(aq) +e- external power sourceexternal power sourceAuAuAu+(aq)Au+(aq)cathode:Au+(aq) +e-→Auanode:Au→Au+(aq) +e-
484-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
49ELECTRO REFINING OF COPPER ELECTROLYTEAqueous copper sulphate solutionELECTRODESCATHODE : pure thin sheet of copperANODE : Impure block of copperIONS PRESENTCuSO Cu2+ + SO42-H2O H+ + OH-REACTION AT THE CATHODECu2+ ions are discharged at the cathode as neutral copper atoms.Cu e CuREACTION AT THE ANODECopper anode itself loses electrons to give Cu2+ ions in solution.Cu Cu e
52Work sheet1. While the experiment is running answer these questions in your note book.Why must the blister copper be purified before use?At the anode copper atoms are going to dissolve. What will they become?Write an equation for this. Is this reaction reduction or oxidation?At the cathode new copper atoms are going to be formed.d) What do you think will happen to the masses of each electrode?
55REFERENCESBOOKS:1- Chemistry ‘A course for O’level’ by Christopher N. Prescott2- New edition chemistry by Richard Harwood3- GCSE chemistry by M.J.Denial4- GCSE chemistry for class X by R D Madan & B.S.Bisht5- Chemistry for class IX, STBBWEBSITES: