Download Chapter 13 Review

Chapter 13
Understanding Concepts
1. Explain the function of the following parts of an
electrolytic cell:
a) electrodes
b) electrolyte
c) external voltage
2. In a voltaic cell, one half-cell has a cadmium electrode
in a 1 mol/L solution of cadmium nitrate. The other
half-cell has a magnesium electrode in a 1 mol/L
solution of magnesium nitrate. Write the cell
notation of the cell.
3. Write the oxidation half-reaction, the reduction
half-reaction, and the overall cell reaction for the
following voltaic cell:
Pt NO(g) NO3-(aq), H+(aq) I-(aq) I2(s), Pt
4. What is the importance of the hydrogen electrode?
5. Lithium, sodium, beryllium, magnesium, calcium,
and radium are all made industrially by the electrolysis
of their molten chlorides. These salts are all soluble
in water, but aqueous solutions are not used for the
electrolytic process. Explain why.
6. Use the following two half-reactions to write balanced
net ionic equations for one spontaneous reaction and
one non-spontaneous reaction. State the standard cell
potential for each reaction:
N2O(g) + 2H+(aq) + 2e– → N2(g) + H2O()
E° = 1.770 V
CuI(s) + e– → Cu(s) + I–(aq) E° = –0.185 V
7. Identify the oxidizing agent and the reducing agent in a
lead-acid battery that is
a) discharging
b) recharging
8. Rank the following in order from most effective to least
effective oxidizing agents under standard conditions:
Zn2+(aq), Co3+(aq), Br2(), H+(aq)
9. Rank the following in order from most effective to least
effective reducing agents under standard conditions:
H2(g), Cl–(aq), Al(s), Ag(s)
10. The ions Fe2+(aq), Ag+(aq), and Cu2+(aq) are present in
the half-cell that contains the cathode of an electrolytic
cell. The concentration of each of these ions is 1 mol/L.
If the external voltage is very slowly increased from zero,
in what order will the three metals Fe, Ag, and Cu begin
to be plated onto the cathode? Explain your answer.
522 MHR • Unit 6 Electrochemical Changes
Applying Concepts
11. Write the half-reactions and calculate the standard cell
potential for each reaction. Identify each reaction as
spontaneous or non-spontaneous:
a) Zn(s) + Fe2+(aq) → Zn2+(aq) + Fe(s)
b) Cr(s) + AlCl3(aq) → CrCl3(aq) + Al(s)
c) 2AgNO3(aq) + H2O2(aq) →
2Ag(s) + 2HNO3(aq) + O2(g)
12. a) Describe a method you could use to measure the
standard cell potential of the following voltaic cell:
Sn(s) Sn2+(aq)(1 mol/L) Pb2+(aq)(1 mol/L) Pb(s)
b) Why is this cell unlikely to find many practical uses?
13. The two half-cells in a voltaic cell consist of one iron
electrode in a 1 mol/L iron(II) sulfate solution, and a
silver electrode in a 1 mol/L silver nitrate solution.
a) Assume the cell is operating as a voltaic cell. State
the cell potential, the oxidation half-reaction, the
reduction half-reaction, and the overall cell reaction.
b) Repeat part (a), but this time, assume that the cell is
operating as an electrolytic cell.
c) For the voltaic cell in part (a), do the mass of the
anode, the mass of the cathode, and the total mass
of the two electrodes increase, decrease, or stay the
same while the cell is operating?
d) Repeat part (c) for the electrolytic cell in part (b).
14. a) Describe an experiment you could perform to
determine the products from the electrolysis of
aqueous zinc bromide. How would you identify the
electrolysis products?
b) Zinc and bromine are the observed products from
the electrolysis of aqueous zinc bromide solution
under standard conditions. They are also the
observed products from the electrolysis of molten
zinc bromide. Explain why the first observation is
surprising.
15. Use the half-cells shown in a table of standard
reduction potentials. Could you build a battery with a
potential of 8 V? If your answer is yes, give an example.
16. Research the following information. Prepare a short
presentation or booklet on the early history of
electrochemistry: ICT
a) the contributions of Galvani and Volta to the
development of electrochemistry
b) how Humphry Davy and Michael Faraday explained
the operation of voltaic and electrolytic cells (note:
these scientists could not describe them in terms
of electron transfers, because the electron was not
discovered until 1897)