Balancing Equations - Set #1
Solution Set
Balance the following equations using the change-in-oxidation state (electron transfer) method:
-2
0 +4 (red: + 2 e-1) x1 +6 -1
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1. 1 I2 + 1 H2SO3 + 1 H2O 1 H2SO4 + 2 HI
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(oxid: - 2 e-1) x1
+3 +2 (oxid: - 1 e-1) x2 +3 +4
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2. 2 FeCl3 + 1 SnCl2 2 FeCl2 + 1 SnCl4
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(red: + 2 e-1) x1
+4 +6
+5 (+2)x2 (oxid: - 2 e-1) x3 (+3)x2 -1
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3. 1 KClO3 + 6 FeSO4 + 3 H2SO4 3 Fe2(SO4)3 + 1 KCl + 3 H2O
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(red: + 6 e-1) x1
-2 +1 (oxid: - 8 e-1) x1 +1 +6
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4. 1 H2S + 4 NaClO 4 NaCl + 1 H2SO4
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(red: + 2 e-1) x4
+5 0 (oxid: - 1 e-1) x3 +2 +1
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5. 4 HNO3 + 3 Ag 1 NO + 3 AgNO3 + 2 H2O
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(red: + 3 e-1) x1
+5 -2 (red: + 3 e-1) x2 0 +2
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6. 8 HNO3 + 3 Ag2S 3 S + 6 AgNO3 + 2 NO + 4 H2O
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(oxid: -2 e-1) x3
+2 -2 +5 (red: + 3 e-1) x1 +3 +2 0
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7. 1 FeS + 4 HNO3 1 Fe(NO3)3 + 1 NO + 1 S + 2 H2O
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(oxid: -1 e-1) x1
(oxid: -2 e-1) x1
0 (red: + 2 e-1) x5 -2 +10
| -1| +5
8. 6 Ca(OH)2 + 6 Cl2 5 CaCl2 + 1 Ca(ClO3)2 + 6 H2O
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(oxid: -10 e-1) x1
Balance the following equations using the half-cell (ion-electron) method:
9. 3 FeCl2 + 3 HCl + 1 HNO3 à 3 FeCl3 + 1 NO + 2 H2O
Oxid: [ Fe+2 à Fe+3 + 1 e-1 ] x 3
Red: [ 3 e-1 + 4 H+1 + NO3-1 à NO + 2 H2O ] x 1
10. 1 K2Cr2O7 + 3 H2S + 8 HCl à 2 KCl + 2 CrCl3 + 3 S + 7 H2O
Oxid: [ S-2 à S + 2 e-1 ] x 3
Red: [ 6 e-1 + 14 H+1 + Cr2O7-2 à 2 Cr+3 + 7 H2O ] x 1
11. 2 KMnO4 + 5 NaNO2 + 6 HCl à 2 KCl + 2 MnCl2 + 5 NaNO3 + 3 H2O
Oxid: [ H2O + NO2-1 à NO3-1 + 2 H+1 + 2 e-1 ] x 5
Red: [ 5 e-1 + 8 H+1 + MnO4-1 à Mn+2 + 4 H2O ] x 2
12. 3 Br2 + 6 NaOH à 1 NaBrO3 + 5 NaBr + 3 H2O
Oxid: [ 6 OH-1 + Br à BrO3-1 + 3 H2O + 5e-1 ] x 1
Red: [ 1 e-1 + Br à Br-1 ] x 5
Balance by any method that you wish:
13. 2 C3H6 + 9 O2 à 6 CO2 + 6 H2O
14. 3 BaCl2 + 2 H3PO4 à 6 HCl + 1 Ba3(PO4)2
Balancing Equations - Set #2
Solution Set
Balance the following equations using the change-in-oxidation state (electron transfer) method:
-2 +5 (red: + 3 e-1) x2 0 +2
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1. 3 H2S + 2 HNO3 3 S + 2 NO + 4 H2O
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(oxid: - 2 e-1) x3
2. 8 HI + 1 H2SO4 4 I2 + 1 H2S + 4 H2O
3. 2 HBr + 1 H2SO4 1 Br2 + 1 SO2 + 2 H2O
4. 2 KMnO4 + 16 HBr à 5 Br2 + 2 MnBr2 + 2 KBr + 8 H2O
5. 2 KMnO4 + 5 H2S + 3 H2SO4 à 5 S + 2 MnSO4 + 1 K2SO4 + 8 H2O
+12 +6
+6 +3
6. 1 K2Cr2O7 + 3 H2S + 4 H2SO4 à 3 S + 1 Cr2(SO4)3 + 1 K2SO4 + 7 H2O
7. 1 S + 2 H2SO4 3 SO2 + 2 H2O
0 -5 +5 -1
8. 6 NaOH + 3 Br2 1 NaBrO3 + 5 NaBr + 3 H2O
+1
9. 1 Cd + 4 HNO3 1 Cd(NO3)2 + 2 NO2 + 2 H2O
Balance the following equations using the half-cell (ion-electron) method:
10. 1 Pb + 4 H+ + 2 NO3-1 1 Pb+2 + 2 NO2 + 2 H2O
Oxid: [ Pb à Pb+2 + 2 e-1 ] x 1
Red: [ 1 e-1 + 2 H+1 + NO3-1 à NO2 + 1 H2O ] x 2
11. 2 MnO4 -1 + 16 H+ + 10 Cl -1 à 2 Mn+2 + 5 Cl2 + 8 H2O
Oxid: [ 2 Cl-1 à Cl2 + 2 e-1 ] x 5
Red: [ 5 e-1 + 8 H+1 + MnO4-1 à Mn+2 + 4 H2O ] x 2
12. 1Cr2O7 -2 + 14 H+ + 3 S -2 à 2 Cr +3 + 3 S + 7 H2O
Oxid: [ S-2 à S + 2 e-1 ] x 3
Red: [ 6 e-1 + 14 H+1 + Cr2O7-2 à 2 Cr+3 + 7 H2O ] x 1
13. 2 Cr +3 + 16 OH-1 + 3 Br2 à 2 CrO4 -2 + 6 Br -1 + 8 H2O
oxid: 8 OH-1 + Cr +3 à CrO4 -2 + 4 H2O + 3 e-1 ]x2
red: 2 e-1 + Br2 à 2 Br -1 ]x3
14. 3 Cl2 + 6 OH-1 à 1 ClO3 -1 + 5 Cl -1 + 3 H2O
Balance by any method that you wish:
15. 1 C3H8 + 5 O2 3 CO2 + 4 H2O
16. 2 C6H14 + 19 O2 12 CO2 + 14 H2O
Balancing Equations
Worksheet #3 Solution Set
Balance each of these equations by both methods - change-in-oxidation state and half-cell:
+7 (red: + 5 e-1) x 2
| -2 0 |
1. 2 KMnO4 + 16 HBr à 5 Br2 + 2 MnBr2 + 2 KBr + 8 H2O
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(oxid: - 2 e-1) x 5
oxidation half-reaction: [ Br2 à 2 Br-1 + 2 e-1 ] x 5
reduction half-reaction: [ 5 e-1 + 8 H+1 + MnO4-1 à Mn+2 + 4 H2O ] x 2
2. 1 Cu2S + 14 HNO3 à 2 Cu(NO3)2 + 1 H2SO4 + 10 NO2 + 6 H2O
oxidation half-reaction: [ S-2 + 4 H2O à SO4-2 + 8 H+1 + 8 e-1 ] x 1
[ 2 Cu+1 à 2 Cu+2 + 2 e-1 ] x 1
reduction half-reaction: [ 1 e-1 + 2 H+1 + NO3-1 à NO2 + H2O ] x 10
3. 16 KOH + 2 CrCl3 + 2 Cl2 à 2 K2CrO4 + 12 KCl + 8 H2O
oxidation half-reaction: [8 OH-1 + Cr+3 à CrO4-2 + 4 H2O + 3 e-1 ] x 2
reduction half-reaction: [ Cl2 + 2 e-1 à 2 Cl-1 ] x 3
4. 3 Cd + 8 H+1 + 2 NO3-1 à 3 Cd+2 + 2 NO + 4 H2O
oxidation half-reaction: [ Cd à Cd+2 + 2 e-1 ] x 3
reduction half-reaction: [ 3 e-1 + 4 H+1 + NO3-1 à NO + 2 H2O ] x 2
-2-
5. 2 KMnO4 + 5 H2O2 + 3 H2SO4 à 5 O2 + 2 MnSO4 + 1 K2SO4 + 8 H2O
6. 2 FeS + 2 HNO3 + 3 H2SO4 à 1 Fe2(SO4)3 + 2 NO + 2 S + 4 H2O
7. 4 Zn + 10 HNO3 à 4 Zn(NO3)2 + 1 NH4NO3 + 3 H2O
8. 2 NaCrO2 + 2 NaOH + 3 H2O2 à 2 Na2CrO4 + 4 H2O
Na : a + b = 2d O : 2a + b + 2c = 4d + e
Cr : a = d H : b + 2c = 2e
let a = 1, then d also = 1; for Na: 1 + b = 2; then b = 1
for O: 2 + 1 + 2c = 4 + e => 2c = e + 1 e + 1 = 2e - 1 è e = 2
for H: 1 + 2c = 2e => 2c = 2e - 1 then c = 3/2
9. 3 As2S5 + 10 HNO3 + 4 H2O à 6 H3AsO4 + 15 S + 10 NO
10. 10 Fe3O4 + 2 KMnO4 + 48 H2SO4 à 15 Fe2(SO4)3 + 2 MnSO4 + 1 K2SO4 + 48 H2O