Humboldt State University ® Department of Chemistry

Richard A. Paselk

	Introductory Chemistry	Spring 2007
Exercise: Redox Balancing	© R. Paselk 2005
	Worked Examples
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REDOX EQUATION BALANCING PRACTICE PROBLEMS

1)         Balance these reactions in aqueous acidic solutions:

            a)         MnO₄^- + Fe²⁺    Fe³⁺  +  Mn²⁺ 

            b)         H₂O₂  +  MnO₄^- Mn²⁺ +  O_{2 (g)}

            c)         I^-  +  H₂O₂  I₂             

            d)         Cr₂O₇^2-  +  I  Cr³⁺ +  IO₃^-

            e)         S₂O₃^2-  +  I₂  S₄O₆^2- +  I^-

            f)         CuS _(s) +  NO₃^- Cu²⁺ +  S _(s)  +  NO _(g)

            g)         MnO₄^2- MnO_{2 (s)}  +  MnO₄^- 

            h)         Pb _(s)  +  PbO_2(s) +  SO₄^2- PbSO_{4 (s)}

2)        Balance these reactions in aqueous basic solutions:

            a)         Fe(OH)_{2 (s)}   +  MnO₄^-  Fe₂O_{3 (s)}  +  MnO_{2 (s)}

            b)         MnO₄^-  +  HO₂^- MnO_{2 (s)}  +  O_{2 (g)}

            c)         ClO₂  ClO₂^- +  ClO₃^-    

            d)         CrO₄^2-  +  N₂H₄  CrO₂^- +  N_{2 (g)}

            e)         Ag _(s)  +  CN^-  +  O_{2 (g)}  Ag(CN)₂^-

            f)         Co _(s)  +  ClO^-  Co(OH)_{2 (s)}  +  Cl^-

(Answers)