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Redox Reactions : HALF REACTIONS

Redox Reactions : HALF REACTIONS. Day 2. Electrochemical Reactions. REDOX REACTIONS. REACTIONS. Day 1: Using Oxidation numbers. REDOX REACTIONS. Redox reactions are characterized by ELECTRON TRANSFER between an electron donor and electron acceptor. Transfer leads to—

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Redox Reactions : HALF REACTIONS

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  1. Redox Reactions:HALF REACTIONS Day 2

  2. Electrochemical Reactions REDOX REACTIONS REACTIONS Day 1: Using Oxidation numbers

  3. REDOX REACTIONS Redox reactions are characterized by ELECTRON TRANSFER between an electron donor and electron acceptor. Transfer leads to— 1. increase in oxidation number of some element = OXIDATION 2. decrease in oxidation number of some element = REDUCTION

  4. Terminology; Redox Reactions OXIDATION—loss of electron(s) increase in oxidation number. Or called REDUCING AGENT. REDUCTION—gain of electron(s); decrease in oxidation number. Or called OXIDIZING AGENT

  5. LEO says GER Lose electrons: OXIDATION Gain electrons: REDUCTION

  6. Assigning oxidation numbers

  7. Copper + Silver Ion

  8. HALF- REACTIONS Cu(s) + 2 Ag+(aq) ---> Cu2+(aq) + 2 Ag(s) Oxidized? Cu(s) ---> Cu2+(aq) Reduced? 2 Ag+(aq) ---> 2 Ag(s)

  9. Balancing Equations Balance BOTH mass and CHARGE Cu + Ag+ ----> Cu2+ + Ag Step 1:Divide into half-reactions: oxidation and reduction. Ox Cu ---> Cu2+ Red Ag+ ---> Ag

  10. Balancing Equations 1. Balance each for mass (coefficients). Already done in this case. 2. Balance each half-reaction for charge Ox Cu ---> Cu2+ + 2e- (Oxidation electrons OUT: Product) Red Ag+ + e- ---> Ag (Reduction electrons IN: Reactant)

  11. Balancing Equations 3Multiply each half-reaction so the electrons lost equal the number gained Cu ---> Cu2+ + 2e- 2 Ag+ + 2 e- ---> 2 Ag Add the two half reactions to the overall equation. Cu + 2 Ag+ ---> Cu2+ + 2Ag balanced for BOTH charge and mass.

  12. Space Fight Identify two half reactions ID which element reduced and which is oxidized Why are liquid fuel preferred over gaseous? Why use hydrogen and oxygen as fuels if solid fuels provide better propulsion? D8 C10

  13. Redox Equations 2 Al(s) + 3 Cu2+(aq) --> 2 Al3+(aq) + 3 Cu(s)

  14. Recognizing a Redox Reaction 2 Al(s) + 3 Cu2+(aq) --> 2 Al3+(aq) + 3 Cu(s) Al is OXIDIZED Al(s) --> Al3+(aq) + 3 e- Al Ox. # increases (more positive): loses e- : Oxidation Al is the REDUCING AGENT in this half-reaction.

  15. Recognizing a Redox Reaction 2Al(s) + 3Cu2+(aq) ’ 2Al3+(aq) + 3Cu(s) Cu is REDUCED Cu2+(aq) + 2 e- ’ Cu(s) Ox. # of Cu decreases (more neg.) gaining electrons Reduction Cu is the OXIDIZING AGENT in this half-reaction.

  16. Recognizing a Redox Reaction 2 half-reactions add up to give the overall reaction 2 Al(s) --> 2 Al3+(aq) + 6 e- 3 Cu2+(aq) + 6 e- --> 3 Cu(s) -------------------------------------------------- 2 Al(s) + 3 Cu2+(aq) ---> 2 Al3+(aq) + 3 Cu(s) balanced for mass and charge.

  17. “REDOX on Wheels”: Automobiles D8 C13

  18. Ready for more complex reactions? No!

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