BALANCING REDOX REACTIONS

Balance the following equations of redox reactions:

• Assign oxidation numbers to all elements in the reaction
• Separate the redox reaction into two half reactions
• Balance the atoms in each half reaction
• Add the two half-reactions together and cancel out common terms

Balance the following redox equation by the oxidation number methode

...in acidic solution.

1. Ag + HNO3 = AgNO3 + NO2 + H2O
2. Ag2S + HNO3(konc.) = AgNO3 + NO2 + S + H2O
3. Ag2S + HNO3(dil.) = AgNO3 + NO + S + H2O
4. As + HNO3 + H2O = H3AsO4 + NO
5. As + NO3- = As2O5 + NO
6. As2O3 + NO3- = H3AsO4 + N2O3
7. As2S5 + HNO3 = H3AsO4 + NO2 + S + H2O
8. As2S5(s) + HNO3(aq) = H3AsO4(aq) + H2SO4(aq) + NO2(g)
9. Bi2S3 + HNO3 = Bi(NO3)3 + NO + S + H2O
10. CdS + HNO3 = Cd(NO3)2 + S + NO + H2O
11. Cu + HNO3 = Cu(NO3)2 + NO + H2O
12. HNO3 + Cu2O = Cu(NO3)2 + NO + H2O
13. CuS + NO3- = NO + Cu2+ + HSO4-
14. Mg + HNO3 = Mg(NO3)2 + N2 + H2O
15. PbS + HNO3 = Pb(NO3)2 + NO + S + H2O
16. Sn + HNO3 = SnO2 + NO2 + H2O
17. Zn(s) + HNO3(aq) = Zn(NO3)2(aq) + NH4NO3(aq) + H2O(l)
18. Zn + NO3- = NH4+ + Zn2+
19. I2 + HNO3 = HIO3 + NO2 + H2O
20. P4 + HNO3 + H2O = H3PO4 + NO
21. H2S + HNO3 = NO + S + H2O
22. H2S + NO3- = S8 + NO
23. S + HNO3 = H2SO4 + NO2 + H2O
24. HI + HNO3 = NO2 + I2 + H2O
25. HCl + HNO3 = NO2 + Cl2 + H2O
26. Hg + HNO3 = Hg(NO3)2 + NO2 + H2O
27. NO3- + H2O2 = NO + O2
28. NO3- + I2 = IO3- + NO2
29. S2- + NO3- = NO + S8
30. Ru(s) + Cl-(aq) + NO3-(aq) = RuCl63-(aq) + NO2(g)
31. P4 + HNO3 = H3PO4 + NO
32. HNO2 = NO + NO2
33. HNO2 = HNO3 + NO
34. BrO3-(aq) + N2H4(aq) = Br2(l) + N2(g)

...in basic solution.

1. NO3- = N2O + O2
2. Al(s) + NO3- = Al(OH)4- + NH3(g)
3. NO3- + Zn + OH- = NH3 + ZnO22- + H2O
4. Sb2O3(s) + NO3-(aq) = H3SbO4(aq) + NO(g)
5. Al(s) + NO2- (aq) = AlO2- (aq) + NH3(aq)
6. CO2 + NH2OH = CO + N2 + H2O
7. Tl2O3 + NH2OH = TlOH + N2
8. OCN- + OCl- = CO32- + N2 + Cl-
9. NH3 + ClO- = N2H4 + Cl-
10. N2H4 + ClO3- = NO + Cl-
11. N2H4 + Fe(CN)63- + OH- = N2 + Fe(CN)64-
12. Ni(OH)2 + N2H4 = Ni + N2
13. N2H4 + Cu(OH)2 = N2 + Cu

Balance the following redox equation by the ion-electron method

...in acidic solution.

1. KI + KNO2 + H2SO4 = I2 + NO + K2SO4 + H2O
2. KI + H2SO4 = K2SO4 + I2 + H2S + H2O
3. C + H2SO4 = CO2 + SO2 + H2O
4. Cu + SO42- = Cu2+ + SO2
5. CuS(s) + HNO3(aq) = Cu(NO3)2 + S(s) + NO(g) + H2O(l)
6. FeSO4 + H2O2 = Fe2O3 + SO42- + H2O
7. HBr + SO42- = SO2 + Br2
8. H2SO3 + H2O + I2 = HI + H2SO4
9. ClO3- + SO2 = SO42- + Cl-
10. CdS + I2 + HCl = CdCl2 + HI + S
11. H2S + I2 = S + HI
12. S2- + O22- + H+ = SO42- + H2O
13. H2S + H2O + Br2 = HBr + H2SO4
14. HCNS + H2O + Br2 = H2SO4 + HCN + HBr
15. KSCN + H2O + I2 = KHSO4 + HI + ICN
16. Na2S2O3 + I2 = Na2S4O6 + NaI
17. S2O82- + Mn2+ = SO42- + MnO4-

...in basic solution.

1. SO32- + Cr2O72- = Cr3+ + SO42-
2. Cu2+ + SO32- = SO42- + Cu
3. S2O42- + O2(g) = SO42-

Balance the following redox equation by the oxidation number methode

...in acidic solution.

1. AlBr3 + KMnO4 + H2SO4 = Al2(SO4)3 + K2SO4 + MnSO4 + Br2 + H2O
2. HCl + KMnO4 = KCl + MnCl2 + H2O + Cl2
3. FeSO4 + KMnO4 + H2SO4 = Fe2(SO4)3 + K2SO4 + MnSO4 + H2O
4. NaNO2 + KMnO4 + H2SO4 = NaNO3 + K2SO4 + MnSO4 + H2O
5. KMnO4 + H2SO4 + FeSO4 = K2SO4 + MnSO4 + Fe2(SO4)3 + H2O
6. KI + KMnO4 + H2SO4 = MnSO4 + K2SO4 + I2 + H2O
7. HCOOH + MnO4- = CO2 + Mn2+
8. C2O42- + MnO4- = CO2 + Mn2+
9. Na2C2O4 + KMnO4 + H2SO4 = K2SO4 + Na2SO4 + MnSO4 + CO2 + H2O
10. CH3CH2CH2OH + KMnO4 + H2SO4 = CH3CH2COOH + K2SO4 + MnSO4 + H2O
11. CH3OH + MnO4- = CO32- + MnO42-
12. MnO4- + CH3OH = HCOOH + Mn2+
13. MnO4- + H2S = Mn2+ + S8
14. PbO2 + Mn2+ = MnO4- + Pb2+

...in basic solution.

1. Al + MnO4- = MnO2 + Al(OH)4-
2. Br- + MnO4- = MnO2 + BrO3-
3. MnO4- + CH3COH = CH3COOH + MnO2
4. KMnO4 + H2O + CH3CH2CHO = MnO2 + CH3CH2COOH + KOH
5. MnO4- + CN- = MnO2 + CNO-
6. MnO4- + C2O42- = MnO2 + CO2
7. MnO4- + SO32- = MnO2 + SO42-
8. H2O2 + MnO4- = MnO2 + O2
9. MnO4- + H2O + NO2- = MnO2(s) + NO3- + OH-
10. MnO4- + I- = MnO42- + IO3-
11. H2O2 + KMnO4 = MnO2 + KOH + O2 + H2O
12. MnO2 + KOH + O2 = K2MnO4 + H2O
13. Mn2+ + ClO3- = MnO2 + ClO2

Balance the following redox equation by the ion-electron method

...in acidic solution.

1. H5IO6 + Cr = IO3- + Cr3+
2. CrI3 + KOH + Cl2 = K2CrO4 + KIO4 + KCl + H2O
3. Cr2O3 + Na2CO3 + KNO3 = Na2CrO4 + CO2 + KNO2
4. Fe2+ + Cr2O72- + H+ = Fe3+ + Cr3+ + H2O
5. S2- + Cr2O72- + H+ = Cr3+ + S + H2O
6. CH3CH2OH + Cr2O72- + H+ = CH3COOH + Cr3+
7. Cr2O72- + H2C2O4 = Cr3+ + CO2
8. Cr2O72- + C2H4O = CH3COOH + Cr3+
9. Cr2O72- + Br- + H+ = Cr3+ + Br2 + H2O
10. Cr2O72- + H+ + I- = Cr3+ + I2 + H2O

...in basic solution.

1. Cr3+ + H2O2 + OH- = CrO42- + H2O
2. HPbO2- + Cr(OH)3 = Pb + CrO42-
3. Se + Cr(OH)3 = Cr + SeO32-
4. Cr(OH)3 + ClO3- = CrO42- + Cl-
5. Cr(OH)4- + OCl- = CrO42- + Cl-
6. Cr(OH)4- + H2O2 = CrO42- + H2O
7. CrO42- + HSnO2- + H2O = CrO2(s) + H2SnO3(aq) + OH-(aq)

Balance the following redox equation by the oxidation number methode

...in acidic solution.

1. CO + Cl2 = COCl2
2. Cl2 + H2O = HCl + HOCl
3. K2SeO4 + HCl = KCl + H2SeO3 + H2O + Cl2
4. CeO2 + HCl = CeCl3 + H2O + Cl2
5. ClO3- + Cl- = Cl2 + ClO2
6. KClO3 + FeSO4 + H2SO4 = KCl + Fe2(SO4)3 + H2O
7. ClO4- + Cl- = Cl2 + ClO-
8. ClO4- + Sn2+ + H+ = Cl- + Sn4+ + H2O
9. PH3 + I2 = H3PO2 + I-
10. CeO2 + KI + HCl = KCl + CeCl3 + H2O + I2
11. PbO2 + HI = PbI2 + H2O + I2
12. FeCl3 + HI = HCl + FeCl2 + I2
13. KIO3 + KI + H2SO4 = I2 + K2SO4 + H2O
14. IO3- + ClO3- + H+ = I2 + ClO4- + H2O
15. KSCN + I2 + H2O = KHSO4 + HI + ICN
16. KIO4 + KI + HCl = KCl + H2O + I2
17. ICN + HI = HCN + I2
18. H3AsO3 + KBrO3 + HCl = KCl + HBr + H3AsO4
19. KBrO3 + HBr + HCl = KCl + H2O + Br2
20. KBrO3 + HCl + Sb2O3 = KCl + HBr + Sb2O5
21. KBrO3 + HCl + SnCl2 = KBr + H2O + SnCl4
22. BrO3- + Fe2+ = Br- + Fe3+

...in basic solution.

1. Cl2O7 + H2O2 = ClO2- + O2
2. Cl2 = Cl- + ClO3-
3. Pb(OH)42- + ClO- = PbO2 + Cl- + OH-
4. N2O(g) + KClO(aq) + KOH(aq) = KCl(aq) + KNO2(aq) + H2O(l)
5. ClO2 + H2O + KOH = H2O + KClO2 + O2
6. ClO2 + OH- = ClO2- + ClO3- + H2O
7. ClO2 + O22- = ClO2- + O2
8. Cl2 + OH- = ClO3- + Cl- + H2O
9. Cl2 + IO3- + OH- = IO4- + Cl- + H2O
10. I- + OCl- = I2 + Cl- + H2O
11. IO3- + I- + OH- = I2 + H2O
12. H2O2 + KI = KOH + I2
13. Cr(OH)3 + Br2 = CrO42- + Br-
14. Br2 = Br- + BrO3-
15. Br2 + KOH = KBr + KBrO3 + H2O

Balance the following redox equation by the ion-electron method

...in acidic solution.

1. C7H6O2 + O2 = CO2 + H2O
2. CH3CH2CH2CHOH + O2 = CO2 + H2O
3. Ce(SO4)2 + C2O4H2 = Ce2(SO4)3 + H2SO4 + CO2
4. Co(NH3)62+ + H+ + O2 = Co(NH3)63+ + H2O
5. O2 + As = HAsO2 + H2O
6. Fe + HCl = HFeCl4 + H2
7. Fe2O3 + CO = Fe + CO2
8. Fe2+(aq) + SiO44-(aq) + O2(g) = Fe2O3(s) + SiO32-(aq)
9. PbS + H2O2 = PbSO4 + H2O
10. Cu+ = Cu2+ + Cu
11. SnCl2 + HgCl2 = SnCl4 + Hg2Cl2
12. CuSO4 + Na = Na2SO4 + Cu
13. Ca3(PO4)2 + SiO2 + C = CaSiO3 + CO2 + P4
14. ZnS(s) + O2(g) = ZnO(s) + SO2(g)

...in basic solution.

1. Ag(s) + CN-(aq) + O2(aq) = Ag(CN)2- + OH-(aq)
2. AlH4- + H2CO = Al3+ + CH3OH
3. Al + NaOH = Na3AlO3 + H2
4. Au + O2 + CN- = Au(CN)2- + H2O2
5. Bi(OH)3 + SnO22- = SnO32- + Bi
6. Fe(OH)2 + H2O2 = Fe(OH)3
7. Mg + NiO2 = Mg(OH)2 + Ni(OH)2
8. O2 + Sb = H2O2 + SbO2-
9. NiO2 + H2O + Fe = Ni(OH)2 + Fe(OH)2
10. Bi(OH)3 + Sn(OH)3- = Sn(OH)62- + Bi
11. P + OH- = PH3 + H2PO2-
12. P4 + OH- + H2O = PH3 + H2PO2-
13. HXeO4- + Pb = Xe + HPbO2-
14. HXeO4-(aq) + OH-(aq) = XeO64-(aq) + Xe(g) + H2O(l)

Convert the following redox reactions to the ionic form.
Balance redox equations using the ion-electron method in an acidic solutions.

1. H2S + KMnO4 = K2SO4 + MnS + H2O + S
2. H2SO3 + KMnO4 = H2SO4 + K2SO4 + MnSO4 + H2O
3. Na2S2O3 + H2O2 = Na2SO4 + H2O + H2SO4
4. Na2S4O6 + H2O2 = Na2SO4 + H2O + H2SO4
5. Mn(NO3)2 + KClO3 + H2O = MnO2*H2O + KNO3 + ClO2
6. KClO3 + HCl = KCl + H2O + Cl2
7. Ca(ClO)2 + KI + HCl = I2 + CaCl2 + H2O + KCl
8. CH3CH2OH + K2Cr2O7 + H2SO4 = CH3COOH + Cr2(SO4)3 + K2SO4 + H2O
9. CuSO4 + KI = CuI + I2 + K2SO4
10. C6H7NO3S + MnO2 + H2SO4 = CO2 + N2 + MnSO4 + H2O
11. MnBr2 + PbO2 + HNO3 = HMnO4 + Pb(BrO3)2 + Pb(NO3)2 + H2O
12. Fe(NO3)2 + HNO3 = Fe(NO3)3 + NO + H2O