Chapter 19 –Redox –Practice Problems
Name: ________________________________________
Example Problem 1
Determining Oxidation Numbers
Determine the oxidation number of each element in the following compound and ion.
a) SrCO3 (strontium carbonate)
b) Cr2O72- (dichromate ion)
1) Determine the oxidation number of the boldface element in each of these compounds.
a) Li2SiO3
c) CaH2
e) K2GeF6
b) Al4C3
d) BeSeO4
f) Al(ClO3)3
2) Determine the oxidation number of the boldface element in each of these ions.
a) PO43c) HSO4e) PuO2+
b) Hg22+
d) PtCl62-
f) TeO32-
3) In each of the following half-reactions, determine the value of x.
a) S6+ + x e-  S2b) 2Brx  Br2 + 2ec) Sn4+ + 2e-  Snx
d) Which of the above half-reactions represent reduction processes?
Example Problem 2
Determining Oxidation and Reduction
State whether or not any oxidation and reduction is occurring, and write the oxidation-reduction half-reactions.
2Al(s) + 3CuCl2(aq)  2AlCl3(aq) + 3Cu(s)
4) For each of the following reactions, identify what is oxidized and what is reduced. Also identify the oxidizing agent and the
reducing agent.
a) Zn + Ni2+  Ni + Zn2+
c) 2NO  N2 + O2
b) 2I- + Br2  I2 + 2Br-
d) 2H2 + S2  2H2S
Example Problem 3
Balancing a Redox Equation by the Oxidation-Number Method
The reaction of antimony with hot sulfuric acid produces antimony(III) sulfate, sulfur dioxide gas, and water, as shown in this
unbalanced equation.
Sb(s) + H2SO4(aq)  Sb2(SO4)3(aq) + SO2(g) + H2O(l)
Balance this redox equation using the oxidation-number method.
5) Use the oxidation-number method to balance these redox equations.
a) Cu2O + NO  CuO + N2
b) Al2O3 + C + N2  AlN + CO
c) Ag + HNO3  AgNO3 + NO + H2O
d) I2 + HClO + H2O  HIO3 + HCl
Example Problem 4
Balancing a Net Ionic Redox Equation
Use the oxidation-number method to balance the net ionic equation for the redox reaction between the permanganate ion and
the chloride ion in acid solution.
MnO4-(aq) + Cl-(aq)  Mn2+(aq) + Cl2(g) (in acid solution)
6) Use the oxidation-number method to balance these net ionic redox equations.
a) Al(s) + Ni2+(aq)  Al3+(aq) + Ni(s)
b) HS-(aq) + IO3-(aq)  I-(aq) + S(s) (in acid solution)
c) I2(s) + HClO(aq)  IO3-(aq) + Cl-(aq) (in acid solution)
Example Problem 5
Balancing a Redox Equation by Half-Reactions
Use the half-reaction method to balance this redox equation.
K2Cr2O7(aq) + HCl(aq)  CrCl3(aq) + KCl(aq) + Cl2(g)
7) Use the half-reaction method to balance these redox equations.
a) I2(s) + H2SO3(aq)  I-(aq) + HSO4-(aq)
b) Fe2+(aq) + MnO4-(aq)  Fe3+(aq) + Mn2+(aq)
ACTIVITY SERIES
c) Zn(s) + Cr2O72-(aq)  Zn2+(aq) + Cr3+(aq)
d) IO3-(aq) + I-(aq)  I2(s)
Metals
Nonmetals
Lithium
Fluorine
Potassium
Chlorine
Barium
Oxygen
Calcium
Bromine
Sodium
Manganese
________________________________ c) F or O as an oxidizing agent
Chromium
Zinc
Iron
________________________________ b) Ag + Cu2+ 
________________________________ c) Br2 + I- 
10) Label each of the following statements about redox as True or False.
________________________________ a) A strong oxidizing agent is itself readily reduced.
________________________________ b) In disproportionation, one chemical acts as both an oxidizing
agent and a reducing agent in the same process.
________________________________ c) The number of moles of chemical oxidized must equal the
number of moles of chemical reduced.
Phosphorus
Aluminum
________________________________ b) Ag+ or Na+ as an oxidizing agent
9) For each of the following incomplete equations, state whether a redox reaction is likely to
occur.
________________________________ a) Mg + Sn2+ 
Sulfur
Magnesium
Hydrogen in steam
Cobalt
Nickel
Tin
Lead
Hydrogen in acid
Copper
Mercury
Silver
Platinum
Gold
INCREASING ACTIVITY
8) For each of the following, identify the stronger oxidizing or reducing agent
________________________________ a) Ca or Cu as a reducing agent
Iodine
Hydrogen in water
Table 1 – Standard Reduction Potentials
Table 2
INCREASING ACTIVITY
Reducing
agents
Li
K
Ca
Na
Mg
Al
Zn
Cr
Fe
Ni
Sn
Pb
H2
H2S
Cu
IMnO42Fe2+
Hg
Ag
NO21BrSO2
Cr3+
ClMn2+
F-
Oxidizing
agents
Li+
K+
Ca2+
Na+
Mg2+
Al3+
Zn2+
Cr3+
Fe2+
Ni2+
Sn2+
Pb2+
H3O+
S
Cu2+
I2
MnO4Fe3+
Hg22+
Ag+
NO31Br2
H2SO4
Cr2O72Cl2
MnO41F2
INCREASING ACTIVITY
RELATIVE STRENGTH
OF OXIDIZING AND
REDUCING AGENTS