1 / 30

Oxidation – Reduction (Redox)

Oxidation – Reduction (Redox). I. Redox. Assigning oxidation numbers Use the periodic chart! O -2 Oxidation Number is -2 K +1 Oxidation Number is +1 Fe Oxidation Number is 0. 11e -. 11p +. Na atom. Oxidation – Loss of Electrons. Iron Rusting: Fe  Fe 3+ + 3 e -

ila-riley
Download Presentation

Oxidation – Reduction (Redox)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Oxidation – Reduction (Redox)

  2. I. Redox • Assigning oxidation numbers • Use the periodic chart! • O-2 • Oxidation Number is -2 • K+1 • Oxidation Number is +1 • Fe • Oxidation Number is 0

  3. 11e- 11p+ Na atom Oxidation – Loss of Electrons • Iron Rusting: • Fe  Fe 3+ + 3 e- • S-2 S + 2 e- 10e- 11p+ 1e- lose 1 electron Na+1ion Electrons on right side of arrow

  4. 18e- 17p+ Reduction – Gain of electrons • Cu+2 + 2 e- Cu • S + 2 e- S-2 17e- 17p+ +1e- gain 1 electron Cl-ion Cl atom Electrons on left side of arrow

  5. Mnemonic device • “LEO the lion says GER!” • LEO = Loss of Electrons is OXIDATION • GER = Gain of Electrons is REDUCTION

  6. Oxidizing agent – the species that causes oxidation the species that is reduced (gains electrons) • Reducing agent – the species that causes reduction the species that is oxidized (loses electrons)

  7. Tin (II) chloride is added to Solid Aluminum 3 Sn + AlCl3 3 2 2 +2 -1 0 0 +3 -1 Al Sn SnCl2 Al  a) Write the balanced equation: SnCl2 + Al b) Assign oxidation numbers to all elements c) Which species is oxidized?__________ Which species is reduced? ___________  d) What is the oxidizing agent?___________ What is the reducing agent? __________

  8. Hydrochloric Acid added to Aluminum  a) Write the balanced equation: HCl + Al b) Assign oxidation numbers to all elements c) Which species is oxidized?__________ Which species is reduced? ___________  d) What is the oxidizing agent?___________ What is the reducing agent? __________ 3 H2 + AlCl3 2 6 2 +1 -1 0 0 +3 -1 Al H HCl Al

  9. II. Writing half-reaction A. Recall: Subatomic particles 29 29 29 29 29 27 Why are electrons lost/gained rather than protons?

  10. B. Oxidation half reactions: LEO Cu0 Cu+2 + 2e- Fe+2  Fe+3 + 1 e- Oxidation number goes up What is the same in these two reactions? Lose electrons

  11. C. Reduction half reactions: GER Cu+2 + 2e- Cu0 Mn+7 + 1e-  Mn+6 S0 + 2e-  S-2 Oxidation number goes down What is the same in these three reactions? Gain electrons

  12. III. Write the oxidation and reduction half reactions from this equation: Ca + S  Ca+2 + S-2 Oxidation Ca  Ca+2 + 2 e- Reduction S + 2 e- S-2

  13. IV. Vocabulary 1. electricity – Flow of electrons 2. voltage – “Force” causing the flow of electrons 3. anode – oxidation reaction 4. oxidation potential – voltage due to oxidation reaction AN OX

  14. IV. Vocabulary (cont.) 5. cathode – reduction reaction 6. reduction potential – voltage due to reduction reaction (switch sign) 7. net voltage – oxidation potential + reduction potential 8. spontaneous reactions - a reaction that occurs on its own positive net voltage

  15. V. Will Sn + Mg+2 react or Mg + Sn+2 ? look on Oxidation ½-rxn chart… Sn  Sn2+ + 2e- V = 0.14 V Mg  Mg2+ + 2e- V = 2.37 V Which reaction can be flipped so the net voltage is still positive ? Sn2+ + 2e- Sn V = - 0.14 V Mg  Mg2+ + 2e- V = 2.37 V Sn2++ Mg  Sn + Mg2+ V = 2.23 V

  16. Will Cu + Ag+1 react or Ag + Cu+2 ? look on Oxidation ½-rxn chart… Cu  Cu2+ + 2e- V = -0.34 V Ag  Ag+1 + 1e- V = -0.80 V Which reaction can be flipped so the net voltage is still positive ? Ag+1 + 1e-  Ag V = 0.80 V Cu  Cu2+ + 2e- V = -0.34 V 2Ag+ + Cu  2Ag + Cu2+ V = 0.46 V 2 2 2

  17. Review If reverse the reaction, what happens to V? If change coefficients, what happens to V?

  18. VI. Electrochemical cells and batteries Electron flow Anode – Oxidation Reaction Zn Zn2+ + 2e- Cathode – Reduction Reaction Cu+2 + 2e- Cu Zn  Zn2+ + 2e- V = 0.76 V Cu2+ + 2e-  Cu V = 0.34 Cu2+ + Zn  Zn2++ Cu V = 1.10 V

  19. Copper Zinc Electrochemical Cell e- V Salt bridge Cu Zn Zn2+ Cu2+

  20. Zn  Zn2+ + 2e- V = 0.76 V Cu2+ + 2e-  Cu V = 0.34 Cu2+ + Zn  Zn2++ Cu V = 1.10 V

  21. VII. If you created a Zn-Ag battery a. Which element will oxidize? Zinc will oxidize (higher up the table) b. Identify the anode and the cathode. Zn = Anode Ag = Cathode c. Write the half reactions. Zn  Zn+2 + 2e- 0.76 V 2 Ag+ + 2e- 2 Ago 0.80 V d. Calculate the net voltage. 1.56 V

  22. VIII. If you created a zinc/iron (II) battery a. Which element will oxidize? Zinc will oxidize (higher up the table) b. Identify the anode and the cathode. Zn = Anode Fe = Cathode c. Write the half reactions. Zn  Zn+2 + 2e-0.76 V Fe+ + 2e- Fe+2 -0.44 V d. Calculate the net voltage. 0.32 V

  23. IX. Galvanized iron Wrapped in Zinc. Which is more likely to oxidize, or ? A “sacrificial” metal like zinc is oxidized, the structural metal, Fe, remains pure Fe Zn

  24. X. Underground storage tanks (iron) • Use sacrificial metals to keep structural metals from oxidizing

  25. XI Aluminum wiring – a fire hazard?? • Aluminum Wire and Copper Connections • Mostly in houses built between 1965-1973 • Battery effect • Gaps from lost metal then lead to sparks, a fire hazard. http://images.google.com/imgres?imgurl=http://www3.telus.net/metrohomeinspections/images/burned_outlet.jpg&imgrefurl=http://www3.telus.net/metrohomeinspections/aluminum.htm&h=132&w=199&sz=5&hl=en&start=20&sig2=8KgC_kYwotKxkR4tQ1DnSw&um=1&tbnid=LVV-n0RtI_83WM:&tbnh=69&tbnw=104&ei=8OVBRofGHo3oiQGWq93aDA&prev=/images%3Fq%3Daluminum%2Bwiring%2Bfire%26svnum%3D10%26um%3D1%26hl%3Den%26sa%3DN

  26. This is a Copper-nickel pump that was feeding sea water to a pure titanium pump down stream. The galvanic action from the titanium pump pulled most of the copper out of the copper-nickel pump. It was only 2 years old and had to be replaced with a glass composite impeller.

  27. Cell or Battery? Electrochemical Cells combine to make batteries AA, AAA, C, and D “batteries” are really cells = 1.5 V

  28. cell battery

  29. How Can You Get a 9-V Battery?

  30. Inside of a Battery Lithium-Ion Cell Alkaline Cell

More Related