oxidation-reduction

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© Copyright 2002-2007 R.J. Rusay © Copyright 2002-2007 R.J. Rusay Oxidation-Reduction Oxidation-Reduction Dr. Ron Rusay Dr. Ron Rusay Fall 2007 Fall 2007

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Oxidation-Reduction. Dr. Ron Rusay Fall 2007. Oxidation-Reduction. Oxidation is the loss of electrons. Reduction is the gain of electrons. The reactions occur together. One does not occur without the other. - PowerPoint PPT Presentation

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Page 1: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Oxidation-ReductionOxidation-Reduction

Dr. Ron RusayDr. Ron Rusay

Fall 2007Fall 2007

Page 2: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Oxidation-ReductionOxidation-Reduction

�OxidationOxidation is the loss of electrons. is the loss of electrons.�ReductionReduction is the gain of electrons. is the gain of electrons.�The reactions occur together. One does The reactions occur together. One does

not occur without the other.not occur without the other.�The terms are used relative to the The terms are used relative to the

change in the change in the oxidation stateoxidation state or or oxidation numberoxidation number of the reactant(s). of the reactant(s).

Page 3: Oxidation-Reduction
Page 4: Oxidation-Reduction

Oxidation Reduction ReactionsOxidation Reduction Reactions

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

Page 5: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Oxidation StateOxidation State(Oxidation Number)(Oxidation Number)

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

Page 6: Oxidation-Reduction
Page 7: Oxidation-Reduction
Page 8: Oxidation-Reduction

QUESTIONQUESTIONIn which of the following does nitrogen have an oxidation state of +4? 1) HNO3 2) NO2 3) N2O 4) NH4Cl 5) NaNO2

Page 9: Oxidation-Reduction
Page 10: Oxidation-Reduction
Page 11: Oxidation-Reduction
Page 12: Oxidation-Reduction

QUESTIONQUESTIONHow many of the following are oxidation-reduction reactions? NaOH + HCl → + NaCl H2O + 2Cu AgNO3 → 2 + (Ag Cu NO3)2 ( )Mg OH 2 → + MgO H2O N2 + 3H2 → 2NH3 1) 0 2) 1 3) 2 4) 3 5) 4

Page 13: Oxidation-Reduction

Cu 2+ Cu (s)

H2 (g) 2 H +

0

0

+2 e-

- 2 e-

Use oxidation numbers to determine what is oxidized and what is reduced.

Number of electrons gained must equal the number of electrons lost.

- 2 e-

+2 e-

Refer to BalancingOxidation-Reduction Reactions

Page 14: Oxidation-Reduction

QUESTIONQUESTIONIn the reaction 2Cs(s) + Cl2(g) → 2 ( ), CsCl s Cl2 is 1) .the reducing agent 2) .the oxidizing agent 3) oxid .ized 4) .the electron donor 5) two of these

Page 15: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Balancing Redox EquationsBalancing Redox Equationsin acidic solutionsin acidic solutions

1) Determine the oxidation numbers of atoms in both 1) Determine the oxidation numbers of atoms in both reactants and products.reactants and products.

2) Identify and select out those which change 2) Identify and select out those which change oxidation number (“redox” atoms) into separate oxidation number (“redox” atoms) into separate “half reactions”.“half reactions”.

3) Balance the “redox” atoms and charges (electron 3) Balance the “redox” atoms and charges (electron gain and loss must equal!).gain and loss must equal!).

4) In acidic reactions balance oxygen with water 4) In acidic reactions balance oxygen with water then hydrogen from water with acid proton(s).then hydrogen from water with acid proton(s).

1

Page 16: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Balancing Redox EquationsBalancing Redox Equations

FeFe+2+2(aq)(aq)+ Cr+ Cr22OO77

2-2-(aq) (aq) +H+H++

(aq)(aq)---->---->

FeFe3+3+(aq)(aq) + Cr + Cr3+3+

(aq) (aq) + H+ H22OO(l) (l)

??

Fe Fe 2+2+(aq)(aq)+ Cr+ Cr22OO77

2-2-(aq) (aq) +H+H++

(aq)(aq)---->---->

Fe Fe 3+3+(aq)(aq) + Cr + Cr 3+3+

(aq) (aq) + H+ H22OO(l)(l)

1

x x == ?? Cr Cr ; ; 2x+7(-2) 2x+7(-2) = = -2-2; ; x x = = +6+6

Page 17: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Balancing Redox EquationsBalancing Redox Equations

Fe Fe 2+2+(aq)(aq) ---> Fe ---> Fe 3+3+

(aq)(aq)

CrCr22OO772-2-

(aq) (aq) + --> Cr + --> Cr 3+3+(aq) (aq)

CrCr = (= (6+6+))

1

66 (Fe (Fe 2+2+(aq)(aq) -e -e - - ---> Fe---> Fe3+3+

(aq)(aq)))

66 Fe Fe 2+2+(aq)(aq) ---> ---> 6 6 FeFe3+3+

(aq) (aq) + + 6 6 ee - -

CrCr22OO772-2-

(aq) (aq) + 6 e+ 6 e - - --> --> 2 2 CrCr3+3+(aq)(aq)

6 e6 e - -

-e-e - -

22

Page 18: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Balancing Redox EquationsBalancing Redox Equations

66 Fe Fe2+2+(aq)(aq) ---> ---> 6 6 FeFe3+3+

(aq) (aq) + + 6 6 ee - -

CrCr22OO772-2-

(aq) (aq) + 6 e+ 6 e - - --> --> 2 2 CrCr3+3+(aq)(aq)

66 Fe Fe2+2+(aq)(aq)+ Cr+ Cr22OO77

2-2-(aq) (aq) + + ? ? 2nd 2nd HH++

(aq)(aq) ----> ---->

6 6 FeFe3+3+(aq) (aq) + + 2 2 CrCr3+3+

(aq)(aq)+ + ? ? 1st Oxygen 1st Oxygen HH22OO(l) (l)

1

OxygenOxygen == 7 7 2nd (Hydrogen)2nd (Hydrogen) == 1414

Page 19: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Balancing Redox EquationsBalancing Redox Equations

Completely Balanced Equation:Completely Balanced Equation:

66 Fe Fe2+2+(aq)(aq)+ Cr+ Cr22OO77

2-2-(aq) (aq) + + 14 14 HH++

(aq)(aq) ----> ---->

6 6 FeFe3+3+(aq) (aq) + + 2 2 CrCr3+3+

(aq)(aq)+ + 77 HH22OO(l) (l)

1

Page 20: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Balancing Redox EquationsBalancing Redox Equationsin basic solutionsin basic solutions

1) Determine oxidation numbers of atoms in 1) Determine oxidation numbers of atoms in Reactants and ProductsReactants and Products

2) Identify and select out those which change 2) Identify and select out those which change oxidation number into separate “half reactions”oxidation number into separate “half reactions”

3) Balance redox atoms and charges (electron gain 3) Balance redox atoms and charges (electron gain and loss must equal!)and loss must equal!)

4) In basic reactions balance the Oxygen with 4) In basic reactions balance the Oxygen with hydroxide then Hydrogen from hydroxide with hydroxide then Hydrogen from hydroxide with waterwater

1

Page 21: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

MnOMnO2 (aq)2 (aq)+ ClO+ ClO331-1-

(aq) (aq) + OH + OH 1-1-aq) aq) ->->

MnOMnO441-1-

(aq) (aq)+ Cl + Cl 1-1-(aq) (aq) + H+ H22OO(l) (l)

MnMn4+4+ (MnO (MnO22) ---> Mn) ---> Mn7+7+ (MnO (MnO4 4 )) 1-1-

ClCl+5+5 (ClO(ClO3 3 )) 1-1-+ + 6 6 ee-- ---> Cl ---> Cl 1-1-

Balancing Redox EquationsBalancing Redox Equationsin basic solutionsin basic solutions

Page 22: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Electronically Balanced Equation:Electronically Balanced Equation:

22 MnO MnO2 (aq)2 (aq)+ ClO+ ClO331-1-

(aq) (aq) + + 66 e e - - ---->---->

2 2 MnOMnO4 4 1-1- + + Cl Cl 1- 1- + + 6 6 ee--

Balancing Redox EquationsBalancing Redox Equationsin basic solutionsin basic solutions

Page 23: Oxidation-Reduction

© Copyright 2002-2007 R.J. Rusay© Copyright 2002-2007 R.J. Rusay

Completely Balanced Equation:Completely Balanced Equation:

22 MnO MnO2 (aq)2 (aq)+ ClO+ ClO331-1-

(aq) (aq) + + 22 OH OH 1- 1- (aq)(aq)---->---->

2 2 MnOMnO4 (aq)4 (aq)1-1- + + Cl Cl 1- 1-

(aq)(aq)+ + 1 1 HH22O O (l)(l)

99 O in productO in product

Balancing Redox EquationsBalancing Redox Equationsin basic solutionsin basic solutions

Page 24: Oxidation-Reduction

QUESTIONQUESTIONOxalate ion can be found in rhubarb and spinach (among other green leafy plants). The following unbalanced equation carried out in a basic solution, shows how MnO4

– could be used to analyze samples for oxalate.

MnO4– + C2O4

2– MnO2 + CO32– (basic solution)

When properly balanced, how many OH– are present?

1. 12. 23. 34. 4