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Worksheet #11
Chem 106-Fall 2011
1. Balance the following reaction under Acidic Conditions: Zn(s) + Cr2O72-(aq)  Cr3+(aq) + Zn2+(aq)
Electrochemistry
2. Balance the Following Reaction under Basic Conditions:
Al(s) + NO3-(aq)  Al(OH)4-(aq) + NH3(aq)
3. A simple voltaic cell is assembled with Ni(s) and Ni(NO3)2 (aq) in one compartment and Cd(s) and Cd(NO3)2(aq) in the
other compartment. An external wire connects the two electrodes and a salt bridge containing NaNO3 connects the
solutions. The overall reaction is: Ni2+(aq) + Cd(s)  Ni(s) + Cd2+(aq)
a.
b.
c.
d.
e.
With the given information, draw a cell
What is the reaction at the anode?
What is the reaction at the cathode?
What are the directions of electron flow in the external wire and of ion flow in the salt bridge?
Write the cell diagram (notation)
4. The cell diagram for a voltaic cell is: Zn(s) І Zn2+(aq) ІІ Ni2+(aq) І Ni(s). This cell produces a potential E0cell=0.51V under
standard conditions at 25°C. The half cell potential E0(Zn(s)/Zn2+(aq))= -0.76V
a.
b.
c.
d.
Which electrode is the anode?
Which electrode is the cathode?
What will be the direction of electron flow?
Calculate the standard potential for the half cell: Ni2+ + 2e-  Ni(s)
5. Consider the following reduction half reactions:
Half Reaction
Cl2(g) + 2e-  2Cl-(aq)
l2(s) + 2e-  2l-(aq)
Pb2+(aq) + 2e-  Pb(s)
V2+(aq) + 2e-  V(s)
E0 (V)
+1.36
+0.535
-0.126
-1.18
a.
b.
c.
d.
e.
f.
g.
Which is the weakest oxidizing agent?
Which is the strongest oxidizing agent?
Which is the strongest reducing agent?
Which is the weakest reducing agent?
Will Pb(s) reduce V2+(aq) to V(s)?
Will I2(s) oxidize Cl-(aq) to Cl2(g)?
Name the molecules or ions in the rections that can be
reduced by Pb(s)
6. Consider the Following Reaction: Zn2+(aq) + H2(g) +2H2O(l)  Zn(s) + 2H3O+(aq). Using Standard Reduction
Potentials, determine whether this reaction is product favored as written (calculate E0cell and ΔG0). If not how the
reaction should be written?
Half Reaction
Zn (aq) + 2e-  Zn(s)
2H3O+(aq)+ 2e- H2(g) +2H2O(l)
2+
E0 (V)
-0.763
+0.000
7. Calculate the Equilibrium constant for the reaction: Fe(s) + Cu2+(aq)  Fe2+(aq) + Cu(s)
Half Reaction
Cu2+(aq) + 2e-  Cu(s)
Fe2+(aq) + 2e-  Fe(s)
E0 (V)
+0.34
-0.44
8. Consider the following Elctrochemical reaction: Ni2+(aq) + Zn(s)  Ni(s) + Zn2+(aq).
Half Reaction
Zn2+(aq) + 2e-  Zn(s)
Ni2+(aq) + 2e-  Ni(s)
E0 (V)
-0.763
-0.25
a. Calculate the Standard cell potential (E0cell)
b. Find the cell potential if the Ni2+ concentration is 5.0M
and the Zn2+ concentration is 0.050M