Ch.18 - ElectrochemistrySee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Balancing Oxidation-Reduction Reactions

Concept #1: Balancing Redox Reactions

Concept #2: Balancing Acidic Redox Reactions

Practice: Balance the following reaction in an acidic solution. 

Cl2(g) + S2O32-(aq) ---->  Cl-(aq) + SO42-(aq) 

Concept #3: Balancing Basic Redox Reactions

Practice: Balance the following reaction in a basic solution. 

XeO2 (aq) ---->      H2Xe (aq)     +    XeO4 (aq)

Additional Problems
What is the coefficient of the permanganate ion (MnO 4−) when the following equation is balanced? MnO4− + Br − → Mn2+ + Br2          (acidic solution) A) 3                        B) 4                 C) 2                 D) 1                 E) 5
Balance the following redox reaction occurring in acidic solution. (Hint: the Br2 partakes in both half reactions) Br2 (l) → BrO3 (aq) + Br –(aq) 
Balance the following redox reaction in acidic conditions, listing the half reactions for oxidation and reduction. Also list the oxidation states of atoms in reaction.
Consider the reaction of 3.0 M dichromate: Cr2O7 2–      →       Cr3+ (Acidic Medium). What would be the coefficient on water in the balanced equation? a. 7 b. 5 c. 6 d. 4
Consider the equation: Cr2O7 2 – + H + + I –       →      Cr 3+ (aq) + H2O + I 3 – Which coefficient would be needed to balance I –? a) 9               b) 7               c) 5               d) 14
How many electrons are transferred in the following reaction after balancing? (The reaction is unbalanced!) Mg(s) + Al 3+(aq) → Al (s) + Mg2+(aq) A) 1 B) 2 C) 3 D) 4 E) 6
What is the coefficient of the oxidizing agent when it is balanced within a basic solution? Cl2(g) + S2O3 2- (aq)      →       Cl- (aq) + SO4 2- (aq)   a) 1                b) 2                c) 3                d) 4
Balance the following redox reaction in acidic conditions, listing the half reactions for oxidation and reduction. Also list the oxidation states of atoms in reaction.
Balance this ionic equation for a redox reaction, using only whole number coefficients.      ? MnO4- (aq) + ? Fe2+ (aq) + H3O+ (aq) → ? Mn2+ (aq) + ? Fe3+ (aq) + ? H2O (l) What is the coefficient for Fe2+ in the balanced equation? (A) 1 (B) 3 (C) 4 (D) 5
When this oxidation-reduction equation is the balanced in acidic solution, using only whole number coefficients, what is the coefficient for S(s)?  ? Cr2O72- (aq) + ? H2S (aq) → ? Cr3+ (aq) + ? S (s) (A) 4 (B) 3 (C) 2 (D) 1
When the following redox equation is balanced with smallest whole-number coefficients, the coefficient for zinc will be. Zn(s) + ReO4-(aq) → Re(s) + Zn2+(aq) (acidic solution) A) 2 B) 7 C) 8 D) 16 E) None of these choices is correct.
Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of Br2 and OH- in the balanced reaction? Br2(l) → BrO3-(aq) + Br-(aq) A) Br2 = 3, OH - = 6 B) Br2 = 3, OH - = 3 C) Br2 = 2, OH - = 5 D) Br2 = 1, OH - = 2 E) Br2 = 1, OH - = 6
Balance each redox reaction occurring in acidic aqueous solution. a. Zn(s) + Sn2+(aq) → Zn2+(aq) + Sn(s)  
Balance each redox reaction occurring in acidic aqueous solution. b. Mg(s) + Cr3+(aq) → Mg2+(aq) + Cr(s)
Balance each redox reaction occurring in acidic aqueous solution. c. MnO4– (aq) + Al(s) → Mn 2+(aq) + Al 3+(aq)  
Balance each redox reaction occurring in acidic aqueous solution. a. I–(aq) + NO2– (aq) → I2(s) + NO(g)  
Balance each redox reaction occurring in acidic aqueous solution. b. ClO4–(aq) + Cl–(aq) → ClO3–(aq) + Cl2(g)
Balance each redox reaction occurring in acidic aqueous solution. c. NO3– (aq) + Sn2+(aq) → Sn4+(aq) + NO(g)  
Balance each redox reaction occurring in basic aqueous solution. a. MnO4– (aq) + Br –(aq) → MnO2(s) + BrO3– (aq)
Balance each redox reaction occurring in basic aqueous solution. b. Ag(s) + CN–(aq) + O2(g) → Ag(CN)2–(aq)
Balance each redox reaction occurring in basic aqueous solution. c. NO2– (aq) + Al(s) → NH3(g) + AIO2– (aq)
When concentrated H2SO4 (l) is added to I - (aq), I 2 (s) and H2S (g) are formed. When the equation for this reaction is balanced, what is the number of electrons transferred?   a) 8 b) 2 c) 4 d) 6 e) 1 
Balance the following redox reaction by inserting the appropriate coefficients. H+ + CrO42- + NO2- → Cr3+ + H2O +NO3-
Design a voltaic cell from the following half-reactions:     Cr2O7(aq) + 14 H+(aq) + 6 e − → 2 Cr3+(aq) + 7 H2O(l)         E° = 1.33     O2(g) + 4 H+(aq) + 4 e − → H2O(l)                                          E° = 1.23In the overall reaction, how many H + ions would be shown and which side would they be on?A.  18 on the leftB.  16 on the leftC.  10 on the leftD.  10 on the rightE.  12 on the right
Balance the following redox reaction by inserting the appropriate coefficients. HNO3 + H2S → NO +S + H2O
Balance the following redox reaction by inserting the appropriate coefficients.SO42- + NH3 → SO32- + H2O + N2
Balance the following equation:Cu(s) + H+(aq) + NO3-(aq) → NO(g) + H2O(l) + Cu2+(aq)The coefficients are:A) 1,2,1,1,1,1B) 3,2,1,1,1,3C) 3,4,2,2,4,3D) 1,8,2,2,4,1E) 3,8,2,2,4,3
Balance the following equation in acidic conditions. Phases are optional.H3AsO3+ I2 → H3AsO4 + I-(Redox and Oxidation Reactions)
Balance the following equation in acidic conditions. Phases are optional.Cr2+ + H2MoO4 + 4H+ → Cr3+ + Mo + 2H2O
Balance the following redox reaction by inserting the appropriate coefficients.HNO3 + H2S → NO + S + H2O
Balance the following redox reactions occurring in basic solution.MnO4−(aq) + Br -(aq) → MnO2(s) + BrO3−(aq)a. MnO4−(aq) + H2O(l) + Br−(aq) → MnO2(s) + 2OH−(aq) + BrO3−(aq)b. 2MnO4−(aq) +  H2O(l) + Br−(aq) → 2MnO2(s) + 2OH−(aq) + BrO3−(aq)c. 2MnO4−(aq) +  H2O(l) + Br−(aq) → 2MnO2(s) + OH−(aq) + BrO3−(aq)d. MnO4−(aq) +  H2O(l) + 2Br−(aq) → MnO2(s) + OH−(aq) + 2BrO3−(aq)
Balance the following redox reactions occurring in basic solution.NO2−(aq) + Al(s) → NH 3(g) + AlO2−(aq)a. NO2−(aq) + H2O(l) + 2Al(s) + OH−(aq) → NH3(g) + 2AlO2−(aq)b. NO2−(aq) + H2O(l) + 2Al(s) + OH−(aq) → 2NH3(g) + 2AlO2−(aq)c. NO2−(aq) + H2O(l) + Al(s) + 2OH−(aq) → 2NH3(g) + AlO2−(aq)d. NO2−(aq) + 2H2O(l) + Al(s) + 2OH−(aq) → NH3(g) + AlO2−(aq)
Determine whether or not each metal dissolves in 1 M HCl. For those metals that do dissolve, write a balanced redox reaction showing what happens when the metal dissolves.a. Cub. Fec. Au
Determine whether or not each metal dissolves in 1 M HIO 3. For those metals that do dissolve, write a balanced redox equation for the reaction that occurs.a. Aub. Cr
Balance the following equation in basic conditions. Phases are optional. CoCl2 + Na2O2 → Co(OH)3 + Cl- + Na+
Balance the following equation in basic conditions. Phases are optional. SO32- + Co(OH)2 → Co + SO42-
Balance each of the following redox reactions occurring in basic solution.   a. H2O2(aq) + ClO2(aq) → ClO2-(aq) +O2(g) b. Al(s)+MnO4-(aq) → MnO2(s) + Al(OH)4-(aq) c. Cl2(g) → Cl−(aq)+ ClO−(aq)
If a nail made of elemental iron [Fe(s)] is placed in an aqueous solution of a soluble palladium(II) salt [Pd2+ (aq)], the nail will gradually disappear as the iron enters the solution as Fe3+ (aq) and palladium metal [Pd(s)] forms. a. Is this a redox equation? b. Balance and show the net ionic equation that describes this reaction.
In each reaction, find the oxidation number of each atom, label which species is oxidized and which is reduced, and label which species is the reducing agent and which is the oxidizing agent. SrSO4 + 4C → SrS + 4CO Oxidized: _____ Oxidizing Agent: _____ Reduced: _____ Reducing Agent: _____ 
Balance the following equation in basic conditions. Phases are optional.CoCl2 + Na2O2 → Co(OH)3 + Cl- + Na+(redox and oxidation reactions)