CP Chemistry
Unit 8: Redox and Electrochemistry
*The small test/large quiz will be free response (~25-30 points, 45 minutes).
*Review dates: In-class review time, Lunch 5/23, and 7th period 5/27.
*Bring a SCIENTIFIC CALCULATOR to the test (like usual).
*You will get a periodic table, polyatomic ion sheet, and standard reduction potential table for the
test.
**Answer key is posted on my website!
Suggestion: I would treat this like a “practice test” since you have already had ample practice with
the in-class worksheet. Obviously, this practice is much longer than what you would actually get for
the test but these are the types of questions you should expect to see.
Concepts:
 Oxidation numbers
 Oxidation
 Reduction
 Redox reactions
 Half-reactions
o Balancing reactions using the halfreaction method
 Electrochemistry
 Voltaic cell


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o Half-cell
o Electrode
o Anode
o Cathode
o Salt bridge
Cell notation
Reduction potential
Cell potential
Practice Questions:
1. What is a redox reaction? What are transferred in a redox reaction?
2. In a redox reaction, how do you know which species has been oxidized or reduced?
3. What are half-reactions?
4. What is a voltaic cell? How does it work?
5. What is the function of the salt bridge in a voltaic cell?
6. What is reduction potential?
7. What reaction happens at the cathode? At the anode?
8. What does it mean if the cell potential is negative?
Practice Problems: (solutions posted on my website)
1. Assign oxidation numbers:
a. NF3
e. N2H4
i.
(NH4)2(CrO4)
b. Ba(NO3)2
f. MnO2
j.
H3O+
c. ClO4-
g. MgCO3
k. CN-
d. N2O
h. CO
2. Identify the half-reactions and balance the following reactions (*remember, after you balance
the electrons in the half-reactions transfer the coefficients to the original equation. Don’t change
these anymore! If oxygen needs to be balanced, use H2O. If hydrogen needs to be balanced, use
H+):
a. CH4 + O2  CO2 + H2O
b. Ag + NO3- + H+  Ag+ + NO + H2O
c. NaBr + Cl2  NaCl + Br2
d. Al + H+ + Cl-  Al3+ + H2 + 2Cl-
e. Cu + SO42- + H+  Cu2+ + SO2 + H2O
3. Fe2+ + 2e-  Fe
Cu2+ + 2e-  Cu
a. Write the overall cell reaction for the given pair of half-reactions.
b. Write the cell notation.
c. Calculate E0cell.
4. Rb+ + e-  Rb
Au3+ + 3e-  Au
a. Write the overall cell reaction for the given pair of half-reactions.
b. Write the cell notation.
c. Calculate E0cell.
5. Zn2+ + 2e-  Zn
Ag+ + e-  Ag
a. Write the overall cell reaction for the given pair of half-reactions.
b. Write the cell notation.
c. Calculate E0cell.
d. Sketch the voltaic cell. Be sure to label:
 Electrodes
 Solution
 Direction of electron flow
 Anode
 Cathode
 Salt bridge (draw where ions go!)