Redox equations where four half-reactions are required
Example #1: FeS + NO3¯ ---> NO + SO42¯ + Fe3+ [acidic sol.]
Example #2: CrI3 + Cl2 ---> CrO42¯ + IO4¯ + Cl¯ [basic sol.]
Example #3: Sb2S3 + Na2CO3 + C ---> Sb + Na2S + CO
Example #4: CrI3 + H2O2 ---> CrO42¯ + IO4¯ [basic sol.]
Example #5: XO2+ + YO+ ---> X2O43¯ + Y¯ + Y3O72¯ [basic sol.]
Example #6: Bi(NO3)3 + Al + NaOH ---> Bi + NH3 + NaAlO2
Example #7: Cu3P + Cr2O72¯ ---> Cu2+ + H3PO4 + Cr3+
Example #8: As2S3 + NO3¯ ---> H3AsO4 + S + NO
Example #9: As2S3 + NO3¯ ---> H3AsO4 + S8 + NO
Example #10: S8 + O2 ---> SO42¯
Bonus Example: Cr3+ + I¯ + Cl2 ---> CrO42¯ + IO4¯ + Cl¯ (two answers given, both correct)
Problem #1: HNO3 + H3AsO4 + Zn ---> AsH3 + Zn(NO3)2
Problem #2: CNS¯ + MnO4¯ -----> CO2 + NO + SO2 + Mn2+
Problem #3: K2Cr2O7 + HCl -----> KCl + CrCl + CrCl3 + H2O + Cl2
Problem #4: Zn + H3AsO4 + HNO3 ---> AsH3 + Zn(NO3)2 + H2O
Problem #5: Al + NH4ClO4 ---> Al2O3 + HCl + N2 + H2O
Problem #6: Cu + HNO3 ---> Cu(NO3)2 + HNO2 + NO + H2O
Problem #7: H3AsO4 + H2SO4 + NO ---> As2S3 + HNO3 + H2O
Problem #8: NaHSO3 + HCl + H2O2 ---> NaHSO4 + NaCl + SO2 + H2O
Problem #9: ClO3¯ + As2S3 ---> Cl¯ + H2AsO4¯ + HSO4¯
Problem #10: FeC2O4 + KMnO4 + H2SO4 ---> Fe2(SO4)3 + CO2 + MnSO4 + K2SO4 + H2O
Problem #11: K3Fe(SCN)6 + Na2Cr2O7 + H2SO4 ---> Fe(NO3)3 + Cr2(SO4)3 + Na2SO4 + KNO3 + CO2 + H2O
Problem #12: Fe + H2SO4 ---> FeSO4 + Fe2(SO4)3 + H2O + SO2
Problem #13: As2S3 + K2Cr2O7 + H2SO4 ---> H3AsO4 + K2SO4 + Cr2(SO4)3 + H2O
Problem #14: KNO3 + S8 ---> K2S + N2 + O2
Problem #15: Al + NH4ClO4 ---> Al2O3 + AlCl3 + H2O + NO