UNIVERSITY OF ZAMBIA
SCHOOL OF NATURAL SCIENCES
CHEMISTRY DEPARTMENT
Tutorial Sheet 6 2021/2022
Answer ALL questions in an A4 Note Book.
Due Date: 10thJune 2022
1. Iodic acid, HIO3, can be prepared by reacting iodine, I2, with concentrated nitric
acid. The skeleton equation is:
I2(s) + NO3-(aq) → IO3-(aq) + NO2(g).
Balance this equation using the half reaction method.
2. Balance the following equation using the half-rxion method.
H2O2 + ClO2 → ClO2 + O2
(basic solution)
3. Calculate the maximum work available from 50.0 g of aluminum in the following
cell when the cell potential is 1.15 V. Al(s) |Al3+(aq) || H+(aq) | O2(g) |Pt .
Note that O2 is reduced to H2O. Use appropriate standard reduction potentials.
4. Calculate the standard free-energy change at 25°C for the following reaction.
3Cu(s) + 2NO3(aq) + 8H+(aq) → 3Cu2+(aq) + 2NO(g) + 4H2O(l).
Use standard reduction electrode potentials.
5. Calculate the equilibrium constant K for the following reaction at 25°C from
standard electrode potentials. Fe3+(aq) + Cu(s) → Fe2+(aq) + Cu2+(aq).
The equation is not balanced. Use standard reduction electrode potentials.
6. Give the balanced full reaction and calculate the E° for galvanic cells based on the
following reactions. Draw diagrams indicating; the anode, cathode, flow of electrons,
salt bridge
(a) Zn2+(aq)+ 2e-  Zn (s)
Pb2+(aq) + 2e-  Pb(s)
(b) Cr2O7- + 14H+ + 6e-  2Cr3+ + 7H2O
H2O2 + 2H+ + 2e-  2H2O
7. Consider the following half-reactions:
Half-Reaction
MnO4( aq ) + 8 H+ + 5 e-
Mn2+ + 4 H2O
Cr2 O72(aq ) + 14 H+ + 6 eBrO3( aq ) + 6 H+ + 6 e-
Cr3+
+ 7 H2O
E0 (V)
+1.52
+1.33
SO42(aq ) + 4 H+ + 2 e-
��−
SO2(g) + 2 H2O
+0.2
NO3( aq ) + 4 H+ + 3 e-
NO(g) + 2 H2O
+ 0.96
+ 3 H2O
+1.47
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(a) Identify the strongest oxidizing agent and the strongest reducing agent.
(b) Which of the oxidizing agents listed is / are capable of oxidizing ��−
to BrO3( aq ) in acidic solution.
(c) Write a balanced chemical equation for the reaction of Cr2 O72(aq ) and
SO2(g) in acid medium. Is this reaction spontaneous?
(d) Write a balanced chemical equation for the reaction of Cr2 O72(aq ) with
Mn2+(aq) in acid medium. Is this reaction spontaneous?
8. Calculate the missing cell potential.
2.20 V
2FeO4
Fe3+
0.77 V
Fe
Eo
-0.44
2+
Fe
Will Fe3+ disproportionate. Give reasons.
9. Construct a galvanic cell using the following reactions. Look up E° values
(a) MnO4 (aq) - + e→ MnO42-(aq)
(b) Zn 2+(aq) + 2e→ Zn(s)
(i)
(ii)
(iii)
(iv)
What type of electrodes are used at the anode and cathode and why?
Write the reaction at the anode and cathode
Write the overall reaction and calculate the cell potential
Write the line notation for the reaction above
10. Tin is used to coat tin cans for food storage. If the tin is scratched and the iron of
the can exposed, will the iron corrode more rapidly or less rapidly? Explain
11. Compare and contrast the electrolytic and voltaic cell.
12. Explain why different products are obtained in the electrolysis of molten
potassium iodide and in the electrolysis of aqueous solution of potassium iodide.
13. Consider the lead acid battery.
a) What class of battery is it and what distinguishes it from the other
classes of batteries?
b) Give the cell notation for the lead acid battery.
c) Write the half reactions and the discharging reaction of the battery.
d) If each cell in the battery has an output of approximately two volts,
draw a labelled sketch diagram of a battery with a six volt output. On
the diagram indicate the anode and the cathode.
Name one characteristic of an ideal lead-acid battery.