1. Oxidation - Reduction RedOx

2. Oxidation States z... of an element are determined from the number of electrons that are ______ other atoms yGained from yLost to AND yShared with

3. Rules of assigning oxidation states zAtoms have a negative oxidation state if they have the higher e-neg in the bond yNH 3 yN= - 3 yH= + 1 Oxidation states on all the atoms of a molecule & compound must add up to equal zero

4. Uncombined elements free state zElements that are not bonded to a different element have oxidation states of zero. zAl (s) Cu (s) Ag (s) Cl 2 O 2 O 3 Ne

5. zH2SzH2S ysulfur has a -2 oxidation state zH 2 SO 3 ysulfur has a +4 oxidation state zH 2 SO 4 ysulfur has a +6 oxidation state NOW More complicated...

6. Assigning oxidation states to atoms in a polyatomic ion zOxidation states on individual atoms must equal the charge on the ion (SO 4 ) (S +6 O 4 -2 ) -8 +6 = -2 (S O 4 ) = -2 (S O 4 -2 ) -8 = -2

7. Try these... zhydroxide zdichromate zammonium

8. Try these... zHydroxide OH - O= - 2, H= + 1 zDichromate Cr 2 O 7 -2 Cr= + 6, O= - 2 zAmmonium NH 4 +1 N= - 3, H= + 1

9. Assign oxidation states to each atom zNaOH zMnCrO 4 z(NH 4 ) 2 SO 4 zK2O2zK2O2

10. Assign oxidation states to each atom zNaOH Na=+1, O=-2, H=-1 zMnCrO 4 Mn=+2, Cr=+6, O=-2 z(NH 4 ) 2 SO 4 N=-3, H=+1, S=+6, O=-2 zKIO 4 K=+1, I=+7, O=-2 zK 2 O 2 K=+1, O=-1

11. Balancing RedOx reactions using oxidation states zZn + HNO 3 Zn(NO 3 ) 2 + NO 2 + H 2 O Go through the steps on paper…

12. 1. Assign oxidation states to all atoms ydetermine the number of e - lost and gained +4 +3 +2 +1 0 -2 -3 -4 L osing e - o xidation G ain e - R eduction

13. 2. Select product coefficients that balance the e - HINT: switch #’s ybalance major elements with reactants 3. Balance leftovers with inventory * coefficients must be lowest possible whole #s

14. Balance - use oxidation states Cu + HNO 3 Cu(NO 3 ) 2 + H 2 O + NO 3Cu + 8HNO 3 3Cu(NO 3 ) 2 + 4H 2 O + 2NO K 2 Cr 2 O 7 + H 2 O + S SO 2 + KOH + Cr 2 O 3 2K 2 Cr 2 O 7 + 2H 2 O + 3S 3SO 2 + 4KOH + 2Cr 2 O 3

15. Balancing net ionic rxns zMg + Al 3+ Mg 2+ + Al zAl 3+ and Mg +2 are ions zif they give you the charge use it! zIts part of a net ionic rxn y they have removed the spectator ions. Balance for mass and charge

16. Balance... for mass and charge zCu 2+ + K K + + Cu

17. RedOx reactions zChemical reactions involving an electron transfer between reactants

18. Recognizing RedOx zassign oxidation states to the individual elements in reactants and the products if the oxidation state changes for some of the particles it is considered a RedOx reaction Single Replacement Reactions are ALWAYS RedOX Double Replacement Reactions are NEVER RedOX

19. In a RedOx reaction If electrons are lost by one species in a reaction they all MUST be gained by another! zIf one atom is being oxidized another must be reduced. zIn other words... yoxidation and reduction always occur together

20. Oxidation zOxidation results in an increase in oxidation state zAtoms that L ose e - lectrons undergo O xidation Metals tend to undergo oxidation +3 +2 +1 0 -2 -3

21. Reduction zReduction results in a decrease in oxidation state zAtoms which G ain e - lectrons undergo R eduction Non-metals tend to undergo reduction +3 +2 +1 0 -2 -3

22. GeR

23. RedOx: Yes or NO? zHCl + NaOH  HOH + NaCl zMg + 2HCl  MgCl 2 + H 2 zMnO 2 + 4HBr  MnBr 2 + Br 2 + 2H 2 O

24. RedOx: Yes or NO? zHCl + NaOH  HOH + NaCl yNO zMg + 2HCl  MgCl 2 + H 2 yYES zMnO 2 + 4HBr  MnBr 2 + Br 2 + 2H 2 O yYES

25. Al + CuCl 2 ? zWrite a balanced equation based on these reactants. zIs this a RedOx reaction? zWhat species is oxidized? yReduced? Predicting Products of Single Replacement Reactions

26. Al + CuCl 2 ? zWrite a balanced equation based on these reactants. z2Al + 3CuCl 2 2AlCl 3 + 3Cu zIs this a RedOx reaction? YES zWhat species is oxidized? Al 0 yReduced? Cu +2

27. Roaring Animals Often Attack zElements that undergo oxidation cause reduction yReducing agent zElements that undergo reduction cause oxidation yOxidizing agent LEOGER RA OA

28. 2Al + 3CuCl 2 2AlCl 3 + 3Cu zWhat is the Oxidizing Agent? yCu +2 because it gets reduced zWhat is the Reducing Agent? yAl because it gets oxidized These answers always come from the reactant side

29. MnO 2 + 4HCl MnCl 2 + Cl 2 + 2H 2 O zAssign oxidation states to all atoms zWhat species is oxidized? yHow do you know? zWhat species is reduced? yHow do you know?

30. MnO 2 + 4HCl MnCl 2 + Cl 2 + 2H 2 O zAssign oxidation states to all atoms zWhat species is oxidized? Cl -1 yHow do you know? xOxidation state increases from -1 to 0 xCl -1 loses electrons zWhat species is reduced? Mn +4 yHow do you know? xOxidation state decreases from +4 to +2 xMn+4 loses electrons

31. zWhat species is the oxidizing agent? yMn +4 because it gets reduced zWhat species is the reducing agent? yCl - because it gets oxidized

32. RedOx Practice zRemember... +4 +3 +2 +1 0 -2 -3 -4 L osing e - o xidation G ain e - R eduction

33. Writing half-reactions zA half reaction shows either oxidation or reduction of a RedOx reaction. zThe electrons being lost (oxidation) or gained (reduction) are also shown.

34. Oxidation half-reaction zFe (s) Fe +3 (aq) + 3e - zoxidation number increases zelectrons are lost y products zconservation of mass AND CHARGE ycharges on both sides equal each other

35. Reduction half-reaction zSn +4 + 2e - Sn +2 zoxidation number decreases zelectrons are gained yreactants zconservation of mass AND CHARGE ycharges on both sides equal each other

37. Balancing RedOx using 1/2 reactions z1. ASSIGN OXIDATION STATES... z2. Write the oxidation 1/2 reaction z3. Write the reduction 1/2 reaction z4. Balance the two half reactions so that the number of electrons transferred is equal z5. Use these coefficients to balance the RedOx atoms z6. Balance leftover atoms by inventory

38. ... use 1/2 reactions KMnO 4 + HCl  MnCl 2 + KCl + Cl 2 + H 2 O ZnS + O 2  SO 2 + ZnO

39. The End I came... I saw... I RedOxed