PRESENCE OFOXYGENPRESENCE OFWATEROXIDATION OF METALS (METAL LOSEELECTRON TO FORM IONS )Zn  Zn 2++ 2e
NO, RUSTING is a term IS FORIRON ONLYSEA BREEZE CONTAINS DISSOLVESALT (ELECTROLYTE). SORUSTING IS FASTER
KNaMgAlZnFeSnPbCuHgAgAuGold is situated low in ECS,therefore it is a lesselectropositive metalMagnesium is situated higher...
Aluminum is situated high in the electrochemical series.But aluminum is very resistant to corrosion ascompared to iron. Ex...
THE IRON ATOM LOSES ELECTRON TO FORMIRON(II) IONS, Fe 2+Fe  Fe 2++ 2eMetal IRONWATER
STEP 2 ( REDUCTION)E)Where do the electrons that are released byiron flow to? And why?To the other end (positive pole).Bec...
f) What happens to the electron here?Taken by water and oxygenmolecules to form hydroxideions , OH-g) Write half equation ...
h) Where do the hydroxide ionsformed in this reaction go to?Combine with Fe2+STEP 3; FORMATION OF VOLTAICCELLA) What happe...
b) Write ionic equationfor the reactionFe2++ 2OH-Fe(OH)2c) A voltaic cell is formed in this mechanismof rusting. State 2 m...
STEP 4 : FORMATION OF RUSTA) What happen to the iron (II) hydroxideformed when exposed to oxygen?It oxidised rapidly to fo...
Oxidising agent : water and oxygenReducing agent : ironc)State the oxidising agent andreducing agent in rusting mechanism
PREVENTING RUSTING OF IRONWAYS TOCONTROLRUSTINGMETHODS WHERE USED?1.USINGPROTECTIVECOATINGCOVERING WITHPAINT2. COVERING WI...
PREVENTING RUSTING OF IRONWAYS TOCONTROLRUSTINGMETHODS WHERE USED?6. SACRIFICIALPROTECTIONUSING BLOCKS OFZINC METAL7. USIN...
An experiment was done in a lab to investigate factors thataffect rust. All the boiling tubes were left for 3 days
a.After 3 days, it was noticed that in boiling tubesC ,D and E, the potassium hexacyanoferrate(III)solution changed colour...
c.The nails in boiling tubes A and B did notrust. Explaind. Explain the function of experiment in EMagnesium and Zn is mor...
d)Write half reaction for(i) Oxidation ( lose electron) in experiment A(ii) Oxidation ( lose electron ) in experiment C(ii...
f)What type of metals prevent rusting of iron?g)What type of metals encourage rusting ofiron?h)If iron nails are immersed ...
i) Calcium is more effective than zinc toprevent rustingWhy do you think steel objects arecoated with zinc instead of calc...
(ii) In tin plating, iron can is coated with tin.However as soon as the can is scratched, rustingwill occur quickly(iii) I...
Question 1. What is meant by reactivity series ofmetals?Series of metals arrangedaccording to their chemicalreactivity wit...
Question 2. Arrange the following metals according to thereactivity series, in descending ordermagnesiumaluminumpotassiums...
• Question 3 Which substances react with each other? If thesubstances react, write chemical equationsa)Na2O + Mg ……………………...
d)H2 + ZnO………………………………………e)2Fe + 3Ag2O ………………………………………f)CaO + Zn ………………………………………… No reaction6Ag + Fe2O3No reactionH is...
          Reactivity increasesK These metals have very strong attraction towards oxygen, therefore the oxides cannot be re...
How are these metals extracted from their ores? Usethe table above to help youa)Zinc from zinc sulphide Extracted by carbo...
Question 5Zinc is below magnesium in the reactivity series.Can zinc be extracted from zinc oxide usingmagnesium? ExplainQu...
Electrolytic cell Chemical cell/voltaic cellDrawDiagramExample forElectrolysis of copper(II)sulphate using carbonelectrode...
Electrolytic Cell Chemical cellPresence ofvoltmeter orammeter?And why?Ammeter to measurecurrentVoltmeter to measurepotenti...
Electrolytic Cell Chemical CellPositiveelectrodeNegativeelectrodePositiveelectrodeNegativeelectrodeWhere doesOxidationoccu...
Electrolytic Cell Chemical CellWhichelectrode iscathode?(area whereelectrons areaccepted)NEGATIVEELECTRODEPOSITIVEELECTROD...
Redox  part 3= rusting - reactivity series and diff between electrolytic cell and  electrolysis - edited with answers
Redox  part 3= rusting - reactivity series and diff between electrolytic cell and  electrolysis - edited with answers
Upcoming SlideShare
Loading in …5
×

Redox part 3= rusting - reactivity series and diff between electrolytic cell and electrolysis - edited with answers

2,040 views
1,695 views

Published on

questions and answers on redox reactions for rusting, reactivity series and diff between electrolytic cell and electrolysis

Published in: Education, Business, Technology
0 Comments
4 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
2,040
On SlideShare
0
From Embeds
0
Number of Embeds
28
Actions
Shares
0
Downloads
0
Comments
0
Likes
4
Embeds 0
No embeds

No notes for slide

Redox part 3= rusting - reactivity series and diff between electrolytic cell and electrolysis - edited with answers

  1. 1. PRESENCE OFOXYGENPRESENCE OFWATEROXIDATION OF METALS (METAL LOSEELECTRON TO FORM IONS )Zn  Zn 2++ 2e
  2. 2. NO, RUSTING is a term IS FORIRON ONLYSEA BREEZE CONTAINS DISSOLVESALT (ELECTROLYTE). SORUSTING IS FASTER
  3. 3. KNaMgAlZnFeSnPbCuHgAgAuGold is situated low in ECS,therefore it is a lesselectropositive metalMagnesium is situated higherin ECS, so it is a moreelectropositive metal
  4. 4. Aluminum is situated high in the electrochemical series.But aluminum is very resistant to corrosion ascompared to iron. Explain•BECAUSE ALUMINIUM HAS OXIDELAYER WHICH IS VERY TIGHTLY HELD,SO IT WILL PROTECT ALUMINIUMFROM CORROSION.•OXIDE LAYER OF IRON however CANBREAK EASILY
  5. 5. THE IRON ATOM LOSES ELECTRON TO FORMIRON(II) IONS, Fe 2+Fe  Fe 2++ 2eMetal IRONWATER
  6. 6. STEP 2 ( REDUCTION)E)Where do the electrons that are released byiron flow to? And why?To the other end (positive pole).Because this area lack of electron.
  7. 7. f) What happens to the electron here?Taken by water and oxygenmolecules to form hydroxideions , OH-g) Write half equation for thereaction that occurO2 + 2H2O + 4e 4OH-
  8. 8. h) Where do the hydroxide ionsformed in this reaction go to?Combine with Fe2+STEP 3; FORMATION OF VOLTAICCELLA) What happens to the iron(II) ionsand the hydroxide ions formed fromStep 1 and Step 2?They will combine to form Fe(OH)2
  9. 9. b) Write ionic equationfor the reactionFe2++ 2OH-Fe(OH)2c) A voltaic cell is formed in this mechanismof rusting. State 2 movements that producethis voltaic celli)Through the metal :Movement of electronsii) Throgh the water :movement of ions
  10. 10. STEP 4 : FORMATION OF RUSTA) What happen to the iron (II) hydroxideformed when exposed to oxygen?It oxidised rapidly to form hydratediron (III) oxide (rust)B)Write the formula of the rustformedFe2O3.x H2O
  11. 11. Oxidising agent : water and oxygenReducing agent : ironc)State the oxidising agent andreducing agent in rusting mechanism
  12. 12. PREVENTING RUSTING OF IRONWAYS TOCONTROLRUSTINGMETHODS WHERE USED?1.USINGPROTECTIVECOATINGCOVERING WITHPAINT2. COVERING WITH OILAND GREASE3. COVERING WITH OILTIN4. COVERING WITHCHROMIUM5. COVERING WITH ZINCMETAL(GALVANIZING)IRON AND STEEL OBJECT,LIKE MOTOCARS,SHIPS,BRIDGE AND STEELIN MACHINERYCANS AND FOODBUMPERS OF MOTOCARSROOF OF HOUSES
  13. 13. PREVENTING RUSTING OF IRONWAYS TOCONTROLRUSTINGMETHODS WHERE USED?6. SACRIFICIALPROTECTIONUSING BLOCKS OFZINC METAL7. USING BLOCKS OFMAGNESIUMMETAL8. ALLOYING MAKINGSTAINLESS STEELBLOCK OF ZINC AREATTACHED TO THE HULL OFTHE SHIPTO PROTECTUNDERGROUND STEELPIPESKNIVES,SPOONS,MEDICALINSTRUMENT
  14. 14. An experiment was done in a lab to investigate factors thataffect rust. All the boiling tubes were left for 3 days
  15. 15. a.After 3 days, it was noticed that in boiling tubesC ,D and E, the potassium hexacyanoferrate(III)solution changed colour to dark blue. What is theinference?Rusting occurs in boiling tubeC,D and Eb. In which boiling tubes did iron nails showrusting?C, D and E
  16. 16. c.The nails in boiling tubes A and B did notrust. Explaind. Explain the function of experiment in EMagnesium and Zn is moreelectropositive than iron. Mg and Znionise to protect iron from rustingAs a control experiment to showthat iron will still rust withoutcontact with other metals becausethe presence of water and oxygen
  17. 17. d)Write half reaction for(i) Oxidation ( lose electron) in experiment A(ii) Oxidation ( lose electron ) in experiment C(iii) Oxidation ( lose electron) in experiment EMg Mg2++ 2eFe Fe2++ 2eFe Fe2++ 2e
  18. 18. f)What type of metals prevent rusting of iron?g)What type of metals encourage rusting ofiron?h)If iron nails are immersed in alkaline solution,the nails do not rust. ExplainMore electropositive than FeLess electropositive than FeHydroxide ions cannot gain the electronsthat are released by iron atoms . No redoxreaction ocur
  19. 19. i) Calcium is more effective than zinc toprevent rustingWhy do you think steel objects arecoated with zinc instead of calcium?j) Explain the followingsi) When a metal corrodes, it undergoesoxidationZn has protective oxide coatingwhich are not broken easilyMetal atom release electronzincsteel
  20. 20. (ii) In tin plating, iron can is coated with tin.However as soon as the can is scratched, rustingwill occur quickly(iii) In galvanizing, iron is coated with a layer ofzinc. When the galvanized iron is scratched,rusting does not occur. Iron is more electropositive thantin. Rusting will occur fasterZn is more electropositive than iron.Iron will not corrodeTinIroncanzincIronZnFeSn
  21. 21. Question 1. What is meant by reactivity series ofmetals?Series of metals arrangedaccording to their chemicalreactivity with oxygen
  22. 22. Question 2. Arrange the following metals according to thereactivity series, in descending ordermagnesiumaluminumpotassiumsodiumcarbonzinchydrogenirontinleadcoppermercurysilverAurum
  23. 23. • Question 3 Which substances react with each other? If thesubstances react, write chemical equationsa)Na2O + Mg ……………………………/b)Mg + CuO  ……………………………………………………….c)C +2PbO  …………………………………………………………..No reactionCu + MgOCO2 + 2PbMg is less reactivethan NaMg is more reactivethan copperC is more reactivethan Pb
  24. 24. d)H2 + ZnO………………………………………e)2Fe + 3Ag2O ………………………………………f)CaO + Zn ………………………………………… No reaction6Ag + Fe2O3No reactionH is less reactivethan ZnFe is more reactivethan AgZn is less reactivethan Ca
  25. 25.           Reactivity increasesK These metals have very strong attraction towards oxygen, therefore the oxides cannot be reduced by Carbon Extraction of metals must be done by electrolysis of molten compoundsNaCaMgAlC  Zn These metals have weak attraction towards oxygen compared to carbon, so the ores can be extracted easily by carbon HFeSnPbCu Weak attraction towards oxygen, therefore heating EXTRACTION OF METALS
  26. 26. How are these metals extracted from their ores? Usethe table above to help youa)Zinc from zinc sulphide Extracted by carbona)Iron from iron(III) oxide Extracted by carbona)Copper from copper(II) sulphide Heating oxides in aira)Aluminum from aluminum oxideElectrolysis of molten compoundsa)Tin from tin(IV) oxide Extracted by carbona)Gold and silver Exist as free metalsHeat zinc sulphide with carbonHeat iron(III) oxide with carbonHeat copper(II) sulphides in airElectrolysis molten aluminiumoxideHeat tin(IV) oxide with carbonExists as free metals
  27. 27. Question 5Zinc is below magnesium in the reactivity series.Can zinc be extracted from zinc oxide usingmagnesium? ExplainQuestion 6Why is carbon the preferred element used to reducemetals and not hydrogen or other metals?-Yes because magnesium is more reactive thanzinccarbon is cheap and easily available
  28. 28. Electrolytic cell Chemical cell/voltaic cellDrawDiagramExample forElectrolysis of copper(II)sulphate using carbonelectrodeCopper(II) sulphateExample forVoltaic cell using copperand zinc as electrodes, andcopper(II) sulphate andzinc sulphate aselectrolytesREDOX REACTION IN ELECTROLYTIC AND CHEMICAL CELL
  29. 29. Electrolytic Cell Chemical cellPresence ofvoltmeter orammeter?And why?Ammeter to measurecurrentVoltmeter to measurepotential differenceChange ofenergyElectrical to chemicalenergyChemical to electricalenergyPositiveelectrodeNegativeelectrodePositiveelectrodeNegativeelectrodeType ofelectrodeElectrodethat isjoined to thepositive partof thebatteryElectrodethat isjoined to thenegativepart of thebatteryLesselectronegative metalbecomes +electrodeMoreelectronegative metalbecomes –electrode
  30. 30. Electrolytic Cell Chemical CellPositiveelectrodeNegativeelectrodePositiveelectrodeNegativeelectrodeWhere doesOxidationoccur ?( release of e-)and write halfequationAt positiveelectrode4OH-2H2O + O2 +4e--- --At negativeelectrodeZn  Zn2++2e-Where doesReductionoccur ?(acceptof e-)and write halfequation--At negativeelectrodeCu2++ 2e-CuAt positiveelectrodeCu2++ 2e-Cu--
  31. 31. Electrolytic Cell Chemical CellWhichelectrode iscathode?(area whereelectrons areaccepted)NEGATIVEELECTRODEPOSITIVEELECTRODEWhich areais anode?(area whereelectrons arereleased)POSITIVEELECTRODENEGATIVEELECTRODE

×