Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have...
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![Page 1: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/1.jpg)
Balancing Redox Equations:
Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing it! : )
Do the following:
___Al + ____HCl ____ AlCl3 + ___ H2
2 6 2 3
Done!
![Page 2: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/2.jpg)
Balancing Redox Reactions:
Another Example: (spectator ions have not been included)
Sn + Ag+ Sn2+ + Ag
1. Assign oxidation numbers.
0 +1 +2 0
Sn + Ag+ Sn2+ + Ag
![Page 3: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/3.jpg)
2. Oxidation occurs when the oxidation number increases. Reduction occurs when the oxidation number decreases. Write the two half reactions.
Oxidation: Sn Sn2+
Reduction: Ag+ Ag
3. Use electrons to balance the charges in the half reactions. In oxidation the electrons appear on the right. In reduction the electrons appear on the left.
![Page 4: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/4.jpg)
Oxidation: Sn Sn2+ + 2e-
Reduction: Ag+ + 1e- Ag
4. If the number of electrons transferred is not equal multiple by a whole number so that the number of electrons lost equals the number gained.
Oxidation: Sn Sn2+ + 2e-
Reduction: (Ag+ + 1e- Ag) x2
![Page 5: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/5.jpg)
5. Add the half reactions:
Oxidation: Sn Sn2+ + 2e-
Reduction: 2Ag+ + 2e- 2Ag
Net Balanced Redox Reaction (notice that the electrons cancel!)
Sn + 2 Ag+ Sn2+ + 2Ag
![Page 6: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/6.jpg)
Steps for Balancing More:
Step 1: Identify and write the two half-reactions.
Step 2: Balance the elements and charges for each half-reaction: 2 a) Balance all the elements except hydrogen and oxygen.
2b) Balance the oxygen atoms by adding H2O to the appropriate side.
2c) Balance the hydrogen by adding H+ to the appropriate side.
2d) Balance the charges by adding electrons to the appropriate side.
Step 3: Multiply one or both of the half-reactions by a whole number so that the number of electrons gained and lost is equal.
Step 4: Combine the half-reactions. Eliminate anything common to the product and reactant sides.
Step 5: Check that all of the elements are balanced and that the total charge on each side is the same.
![Page 7: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/7.jpg)
Example: Balance: MnO4
- + Fe2+ Mn2+ + Fe3+
Step 1:
Reduction: MnO4- Mn2+ Oxidation: Fe2+ Fe3+
+7, -2 + 2 +2 +3
Step 2:
b) MnO4- Mn2+ + 4H2O
c) MnO4- + 8H+ Mn2+ + 4H2O
d) MnO4- + 8H+ + 5e- Mn2+ + 4H2O
![Page 8: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/8.jpg)
Oxidation:
Fe2+ Fe3+ +1e-
Step 3:
MnO4- + 8H+ + 5e- Mn2+ + 4H2O
(Fe2+ Fe3+ +1e-) x5
![Page 9: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/9.jpg)
Step 4:
Reduction: MnO4- + 8H+ + 5e- Mn2+ + 4H2O
Oxidation: 5Fe2+ 5 Fe3+ +5e-
Net Reaction: MnO4- + 8H+ +5Fe2+ Mn2+ + 4H2O + 5 Fe3+
(electrons are cancelled!)
Step 5:
Notice that the final redox equation is balanced by atom and by charge.
![Page 10: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/10.jpg)
Redox reactions are usually too complex to use trial and error method.
Balance the following example that is in an acidic solution (assume the presence of H2O and H+):
HNO3 + Fe2+ Fe3+ + NO2
1. Assign oxidation numbers.
+1+5-2 +2 +3 +4 -2
HNO3 + Fe2+ Fe3+ + NO2
![Page 11: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/11.jpg)
2. Write the half reactions:
Oxidation: Fe 2+ Fe3+
Reduction: HNO3 NO2
3. Balance the half reactions. Use water to balance the oxygen (a), then hydrogen ions to balance the hydrogen(b), then electrons to balance the charges(c).
a)
Oxidation: Fe 2+ Fe3+
Reduction: HNO3 NO2 + H2O
![Page 12: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/12.jpg)
b)
Oxidation: Fe 2+ Fe3+
Reduction: HNO3 + H+ NO2 + H2O
c)
Oxidation: Fe 2+ Fe3+ + 1e-
Reduction: HNO3 + H+ + 1e- NO2 + H2O
![Page 13: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/13.jpg)
4. Multiply the oxidation and reduction equations by whole numbers so that the number of electrons transferred is equal.
Oxidation: Fe 2+ Fe3+ + 1e-
Reduction: HNO3 + H+ + 1e- NO2 + H2O
5. Add the reactions so that electrons cancel.
Net: Fe 2++ HNO3 + H+ Fe3+ + NO2 + H2O
6. Check the equation is balance by charge and atom.
![Page 14: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/14.jpg)
Videos to review the concept:
Watch the following videos to help you balance redox equations:
http://www.youtube.com/watch?v=KIyGr-1snMY&feature=relmfu
http://www.youtube.com/watch?v=-B3RWeC_7oI
http://www.youtube.com/watch?v=TBmwhTzc41o&feature=fvwrel
![Page 15: Balancing Redox Equations: Many redox equations can be balanced through trial and error! You have been doing this for a least two years without even knowing.](https://reader035.fdocuments.in/reader035/viewer/2022070323/56649d9d5503460f94a8760c/html5/thumbnails/15.jpg)
Chapter 20.3- Read pages 645 654
Page 647 #17 & #18
Page 649 #19 & #20
Page 652 #21
Page 654 #22,23,24 & 25
CHAPTER 20
Review the study guide on page 656
Complete the odd numbered questions on page 658
Complete the Standardized Test Prep
Worksheet Redox - 3