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Unit 7: Redox &

Unit 7: Redox &. Electrochemistry. Bell Ringer. What information does the oxidation number give you?. C 3 H 8 O + CrO 3 + H 2 SO 4  Cr 2 (SO 4 ) 3 + C 3 H 6 O + H 2 O. Electrical production (batteries, fuel cells). REDOX reactions are important in …. Purifying metals (e.g. Al, Na, Li).

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Unit 7: Redox &

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  1. Unit 7: Redox & Electrochemistry

  2. BellRinger What information does the oxidation number give you?

  3. C3H8O + CrO3 + H2SO4 Cr2(SO4)3 + C3H6O + H2O • Electrical production (batteries, fuel cells) REDOX reactions are important in … • Purifying metals (e.g. Al, Na, Li) • Producing gases (e.g. Cl2, O2, H2) • Electroplating metals Why electrochemistry? • Protecting metals from corrosion • Balancing complex chemical equations • Sensors and machines (e.g. pH meter)

  4. REDOX stands for REDuction/OXidation • Oxidation is often thought of as a combination of a substance with oxygen (rusting, burning) • Oxidation refers to a loss of e- • Reduction refers to a gain of e- Remember: LEO the lions says GERRRRRR! LossElectrons= Oxidation Gain Electrons = Reduction What is Redox?

  5. Reactions Fe Fe+3 +3e- What is happening to the Fe atom? Fe is going from 0 to +3 oxidation # It must be losing electrons Loss of Electrons = Oxidation In conclusion, the iron atom is being oxidized

  6. Reactions S +2e-S-2 What is happening to the Sulfur atom? S is going from 0 to -2 oxidation # It must be gaining electrons Gain of Electrons = Reduction In conclusion, the sulfur atom is being reduced

  7.   Na0 H20 F20 - the charge an atom would have if the electrons belonged to the more EN atom - there are a few rules to help us out 1. FREE ELEMENTS Always have an oxidation number of zero Na H2 OxidationNumbers F2

  8. - the charge an atom would have if the electrons belonged to the more EN atom 4. HYDROGEN • H is ALWAYS +1 (for us) • Disclaimer – there are compounds where H has a -1 oxidation number, but we don’t deal with them at this level of chemistry. Oxidation Numbers

  9. - the charge an atom would have if the electrons belonged to the more EN atom 5. OXYGEN • O is ALWAYS -2 (for us) Oxidation Numbers

  10.    Na+1 Ca+2 N-3 S-2 - the charge an atom would have if the electrons belonged to the more EN atom 2. SIMPLE IONS Oxidation Number = the charge an ion would make Sodium ion Calcium ion Sulfur ion Oxidation Numbers Nitrogen ion

  11.  Na+1Cl-1 As+5I5-1  Cu+2(N+5O3-2)2  H2+1Cr2+6O7-2 - the charge an atom would have if the electrons belonged to the more EN atom 3. COMPOUNDS The sum of all oxidation numbers will equal ZERO NaCl AsI5 Cu(NO3)2 OxidationNumbers H2Cr2O7

  12.  (S+6O4-2)-2 (N+5O3-2)-  (Cr2+3O4)-2 - the charge an atom would have if the electrons belonged to the more EN atom 5. POLYATOMIC IONS The sum of oxidation numbers will equal the charge of that ion (SO4)-2 (NO3)- Oxidation Numbers (Cr2O4)-2

  13. Do the five problems on your notes sheet a. Cr2O3 d. KCl b. H2Cr2O7 e. Mg(OH)2 Oxidation Numbers c. AsCl5

  14. BellRinger What things are conserved during a chemical reaction?

  15. Identify in the following reactions what is oxidized and what is reduced 2K + Cl2 2KCl K0 – goes from 0 to +1, it is oxidized What is reduced/oxidized? Cl0 – goes from 0 to -1, it is reduced

  16. Identify in the following reactions what is oxidized and what is reduced 2NaCl + 3SO3 Cl2 + SO2 + Na2S2O7 Cl-1 – goes from -1 to 0, it is oxidized S+6 – goes from +6 to +4, it is reduced Practice

  17. Identify in the following reactions what is oxidized and what is reduced Zn + Pb+2(aq)  Zn+2(aq) + Pb Zn0 – goes from 0 to +2, it is oxidized Pb+2 – goes from +2 to 0, it is reduced Practice

  18. Notes Sheet Practice ID Oxdized and Reduced a. C + H2SO4 CO2 + SO2 + H2O b. HNO3 + HI  NO + I2 + H2O c. KMnO4 + HCl MnCl2 + Cl2 + H2O + KCl d. Sb + HNO3 Sb2O5 + NO + H2O e. HCl + MnO2 MnCl2 + H2O + Cl2

  19. Notes Sheet Practice a. C + H2SO4 CO2 + SO2 + H2O b. HNO3 + HI  NO + I2 + H2O c. KMnO4 + HCl MnCl2 + Cl2 + H2O + KCl d. Sb + HNO3 Sb2O5 + NO + H2O e. HCl + MnO2 MnCl2 + H2O + Cl2

  20. Notes Sheet Practice 1. C + 2Cl2  CCl4 Ox – Red – 2. H2 + Cl2 2HCl Ox – Red – 3. 2P + 3Cl2 2PCl3 Ox – Red – 4. C + H2O  CO + H2 Ox – Red – 5. Fe + 3Cl2 2FeCl2 Ox – Red –

  21. Notes Sheet Practice • 6. 2Al + 3Br2 2AlBr3 • Ox – • Red – • 7. Pb+ 2HCl  PbCl2 + H2 • Ox – • Red – • 8. SiO2+ 2C  Si + 2CO • Ox – • Red – • 9. CO2+ 2Mg  2MgO + C • Ox – • Red – • 10. H2SO4+ Zn  ZnSO4 + H2 • Ox – • Red -

  22. BellRinger Identify what atom is oxidized and what atom is reduced: Fe + 2HCl  FeCl2 + H2

  23. Write both half reactions for the following reaction: Cu + AgNO3 Cu(NO3)2 + Ag Reduction: Ag+ Ag Ag+ + 1e- Ag Oxidation: Cu  Cu+2 HALF REACTIONS Cu  Cu+2 +2e- Cu -2e-  Cu+2

  24. Write both half reactions for the following reaction: HNO3 + I2  HIO3 + NO2 Reduction: N+5 N+4 N+5 + 1e- N+4 Oxidation: I20 I+5 HALF REACTIONS I20 2I+5 +10e- I20 -10e-  2I+5

  25. Half Reactions Write both half reactions for the following reaction: Sn + AgNO3  Sn(NO3)2 + Ag Reduction: Ag+1 Ag0 Ag+1 + 1e- Ag0 Oxidation: Sn0 Sn+2 Sn0 Sn+2 +2e- Sn0 -2e-  Sn+2

  26. Aluminum and Copper Chloride Lab

  27. 2 3 3 2 Redox Lab Al +CuCl2 Cu +AlCl3

  28. BellRinger If you were to react Cu and Nickel(II) Chloride what would the products be? How much metal could you make if you started with 2.00g of Cu?

  29. Oxidizing Agent  - causes the oxidation of another atom - it is actually the atom that is REDUCED - oxidation number decreases - causes the reduction of another atom Reducing Agent  - it is actually the atom that is OXIDIZED - oxidation number increases Ca + Cl2 CaCl2 Oxidizing and Reducing Agents What is the O.A.?  Cl What is the R.A.?  Ca

  30. In the equation below, identify what is oxidized what is reduced. Also identify the oxidizing and reducing agent. 4HCl + MnO2 MnCl2 + 2H2O + Cl2 Oxidized:  Cl- Reduced:  Mn+4 Oxidizing Agent:  Mn+4 PRACTICE Reducing Agent:  Cl-

  31. Electrochemical Reactions Deals with chemical reactions that either produce electricity or need electricity to occur! There are 2 types of ELECTROCHEMICAL CELLS. Some things that are the samefor both types of cells: Anorexic Ox 1. The REDCAT GETS FAT! 2. Electrons always flow from the anode to the cathode!

  32. Zn Cu Zn electrode Cu electrode Half Reactions Cell Type #1 - Voltaic Cell 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- Lose e- (Table J) Gains e- (Table J) Oxidized Reduced Cu+2 Zn+2 Anode (-) Cathode(+) Cu+2 Zn+2 ZnSO4 CuSO4 Will this go on forever?

  33. Zn Cu Zn electrode Cu electrode Half Reactions Cell Type #1 - Voltaic Cell Lose e- (Table J) Gains e- (Table J) Oxidized Reduced Anode (-) Cathode(+) Zn+2 ZnSO4 CuSO4 Will this go on forever?

  34. Zn Cu Zn electrode Cu electrode Gains e- (Table J) Lose e- (Table J) Reduced Oxidized Cathode(+) Anode (-) Electrochemistry Cell Type #1 - Voltaic Cell 2e- 2e- 2e- 2e- Cl- Na+ 2e- Na+ Cl- 2e- Cl- Cl- Na+ Na+ Zn+2 Cu+2 Na+ Cl- Cl- Na+ 2Na+ Zn+2 2Cl- Cu+2 ZnSO4 CuSO4 Zn electrode gets smaller Cu electrode gets bigger

  35. Half Reactions Cell Type #1 - Voltaic Cell

  36. BellRinger In the reaction below, identify what is the oxidizing agent and the reducing agent. Ca + H2O  CaO + H2

  37. Zn Cu Zn electrode Cu electrode Gains e- (Table J) Lose e- (Table J) Reduced Oxidized Cathode(+) Anode (-) Electrochemistry Cell Type #1 - Voltaic Cell 2e- 2e- 2e- 2e- Cl- Na+ 2e- Na+ Cl- 2e- Cl- Cl- Na+ Na+ Zn+2 Cu+2 Na+ Cl- Cl- Na+ 2Na+ Zn+2 2Cl- Cu+2 ZnSO4 CuSO4 Zn electrode gets smaller Cu electrode gets bigger

  38. Electrochemistry Cell Type #1 - Voltaic Cell • Summary: • Voltaic Cells – are spontaneous reactions • Electrons travel through the wire from more reactive metal to the less reactive metal (Table J) • Salt Bridge – permits the flow of ions • Red Cat gets fat!

  39. Electrochemistry Cell Type #2 - Electrolytic Cell These are NOTspontaneous reactions – they areforcedby the addition of electricity! Occur within one container, not two separate cells! These reactions are used to plate metals, purify metals and separate compounds.

  40. Sn Fe Electrochemistry Cell Type #2 - Electrolytic Cell Cathode Anode Becomes negative Becomes positive Picks up + ions from solution Loses positive ion (Sn+2) to solution Gets plated with the metal ion from the solution

  41. BellRinger During a laboratory activity, a student reacted a piece of zinc with 0.1M HCl(aq). Based on Reference Table J, identify one metal that does not react spontaneously with HCl(aq).

  42. Fe K Fe electrode K electrode BellRinger Write out the oxidation and reduction half reactions for the voltaic cell below. (Do not need drawing in notes) NaBr Fe+2 K+1

  43. Electrochemistry Electrochemical Cell Differences Electrolytic Voltaic spontaneous non-spontaneous Anode - negative Anode - positive Needs two containers Needs one container

  44. Fe K Fe electrode K electrode 16. NaBr Packet Review Fe+2 K+1

  45. Al Ag Al electrode Ag electrode 16. Na2SO4 Packet Review Al+3 Ag+1

  46. Cu Zn Electrochemistry Cell Type #2 - Electrolytic Cell Anode Cathode Becomes negative Becomes positive Picks up + ions from solution Loses positive ion (Cu+2) to solution Gets plated with the metal ion from the solution Cu+2 Electrons ALWAYSflow from Anode to Cathode

  47. Electroplating Lab And review packet Electrochemistry

  48. Cu Zn Electrochemistry Cell Type #2 - Electrolytic Cell Anode Cathode Becomes negative Becomes positive Picks up + ions from solution Loses positive ion (Cu+2) to solution Gets plated with the metal ion from the solution Cu+2 Electrons ALWAYSflow from Anode to Cathode

  49. Balancing Net Ionic Equations Done on the board Electrochemistry

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