Oxidation-Reduction
Alexander Darmanin, Marcus
Pabian & Lyn Cheah
Chemistry Stage 6 Syllabus
9.2 Production of Materials
4. Oxidation-reduction reactions are increasingly
important as a source of energy
• identify the relationship between displacement of
metal ions in solution by other metals to the relative
activity of metals
• explain the displacement of metals from solution in
terms of transfer of electrons
• account for changes in the oxidation state of species
in terms of their loss or gain of electrons
Oxidation-Reduction
In oxidation-reduction reactions (redox), changes of oxidation
states occur between chemicals.
3 CuCl2(aq) + 2 Al(s) → ?
•What happens in this reaction?
•What IS an oxidation state?
•What happens to the oxidation states?
•What do YOU know about oxidation-reduction reactions?
Go!
• Materials
1 x 150ml beaker
1 x glass stirring rod
1 x Balance machine
Calculate the grams of Copper
chloride CuCl2 granules
1 x 0.25 g Aluminum foil
50ml distilled water
50ml graduated cylinder
• See work sheet for instructions
Results visible in 5min
• Safety
Wear lab coat, glasses and
gloves
CuCl2 is not that strong but
don’t get It on you – when
done use safe disposal bin
NOT sink
Think
Which of the following best describes a reduction?
A.The loss of electrons during a chemical reaction.
B.The gain of electrons during a chemical reaction.
C.The formation of copper during a chemical reaction.
D.The loss Al during a chemical reaction.
Which of the following best describes oxidationreduction reactions?
A.A reaction that involves the transfer of electrons from one species to
another.
B.A reaction that involves the formation of gases hydrogen and oxygen when
two solutions are mixed.
C.A reaction that involves the formation of solids when two solutions are
mixed.
D.A reaction that involves the neutralisation of H+ ions in solution.
Results – what actually
happens after 20 minutes
Results
In terms of electron transfer:
•In this reaction the Cu2+ ions have been converted into copper atoms
•This requires Cu2+ ion to gain two electrons
•Cu2+(aq) + 2 e- → Cu(s)
•Electrons come from the Al3+
The net result:
•Copper ions come out of solution as Cu metal
•Al goes into solution as an Al3+ ion
•3 Cu2+(aq) + 2 Al(s) → 3 Cu(s) + 2 Al3+(aq)
Half reactions:
•Oxidation is the loss of electrons - Al is oxidised
•Reduction is gain of electrons - Cu2+ is reduced
Simulation:
Reduction of zinc by oxygen:
http://www.youtube.com/watch?v=e6Xxz-VBE6s
Dominant student misconceptions
Oxidation and reduction misconceptions (taken from Garnett & Hackling, 1995 pp84):
6. The oxidation state of an element is the same as the charge of the
monatomic ion of the element.
7. A polyatomic species can be assigned an oxidation state and this equals
the charge on the species.
8. In all chemical equations the "addition" and "removal" of oxygen and
hydrogen can be used to identify oxidation and reduction.
9. In all chemical equations the change in the charges of polyatomic species
can be used to identify oxidation and reduction.
10. Oxidation and reduction processes can occur independently.
What where your Misconceptions???
MORE MISCONCEPTIONS, FULL EXPLANATIONS, SOURCES + SIMULATIONS AT
http://oxidationreductionactivity.wordpress.com
Think
What best describes an oxidation?
What best describes a reduction?
“Not all redox reactions involve oxygen, but all oxidation and reduction
reactions involve transfer of electrons between substances”
-Chemistry and chemical reactivity (6
th
edition) – first year chemistry textbook at UWS
“the increase in oxidation state, is the only one that is universal to all
oxidations”
- Silverstein, 2011
“The only way oxidation-reduction equations can be identified with
certainty is from changes in oxidation states”
- Garnett, Garnett & Hackling, 1995
The theory now
Oxidising agent
Reducing agent
undergoes
undergoes
Oxidation
Gain of electron
Loss of electron
Gain of hydrogen
Loss of hydrogen
Loss of oxygen
Decrease in
oxidising state
But which one of
these definitions is
the most important
and universal in all
redox reactions?
Gain of oxygen
Increase in
oxidising state
can be defined as the
can be defined as the
Reduction
The question is
Electron transfer: Virtual or Literal
Is it just a book keeping strategy
Why is oxidation-reduction only taught as loss or gain of electrons in the
Stage 6 syllabus?
How will this affect further chemistry learning for the students?
YouTube links:
Reduction of zinc by oxygen:
http://www.youtube.com/watch?v=e6Xxz-VBE6s
Patterns of oxidation numbers across the periodic table:
http://www.youtube.com/watch?v=EHe8-AFMsMA
Determining oxidation numbers:
http://www.youtube.com/watch?v=8_CvNPuuhiM&feature=related
Turn copper into gold:
http://www.youtube.com/watch?v=_g_ml8tAnWE&feature=relmfu
The link to our blog again!
http://oxidationreductionactivity.wordpress.com
References
Anselme, J. (1997). Understanding oxidation-reduction in organic chemistry. Journal of Chemical
Education, Volume 74, Number 1, pg. 69 – 72.
Brown, T. L., Lemay, H. E., Bursten, B. E. & Burdge, J. R. (2003). Chemistry The Central Science Ninth
Edition International Edition. Prentice Hall: Australia, pg. 778 – 783.
Cox, A. L. & Cox J. R. (2002). Determining oxidation-reduction on a simple number line. Journal of
Chemical Education, Volume 79, Number 8, pg. 965 – 967.
Garnett, P. J., Garnett, P. J. & Hackling, M. W. (1995). Student’s alternative conceptions in chemistry: A
review of research and implications for teaching and learning. Studies in Science Education,
Volume 25, pg. 69 – 95.
Garnett, P.J. & Treagust, D. F. (1992). Conceptual difficulties experienced by senior high school
studentsof electrochemistry: Electric circuits and oxidation-reduction equations. Journal of
Research in Science Teaching, Volume 29, Number 2, pg. 121 – 142.
Hamza, K. & Wickman, P. (2008). Describing and analyzing learning in action: an empirical study of the
importance of misconceptions in learning science. Science Education, Volume 92, pg. 141 – 164.
Kotz, J.C., Treichel, P. & Weaver, G.C. (2006) Chemistry & chemical reactivity Edition 6th. Thomson
Brooks/Cole: Belmont, California.
Mole, P. (2006). Skepticism in the classroom A high school science teacher in trenches. Skeptic, Volume
12, Number 3, pg. 62 – 70.
Moore, J. T. (2004). Chemistry Made Simple Revised Edition. Made Simple Books: USA, pg. 125 – 129.
Nakhleh, M. B. (1992). Why some students don’t learn chemistry Chemical misconceptions. Journal of
Chemical Education, Volume 69, Number 3, pg. 191 – 196.
Sanger, M. J. & Greenbowe T. J. (1997). Students’ misconceptions in electrochemistry: Current flow in
Electrolyte solutions and the salt bridge. Journal of Chemical Education, Volume 74, Number 7,
pg. 819 – 823.
Sanger, M.J. & Greenbowe T. J. (1999). An analysis of college chemistry textbooks as sources of
misconceptions and errors in electrochemistry. Journal of Chemical Education, Volume 76,
Number6, pg. 853 – 860.
Silverstein, T. P. (2011). Oxidation and reduction: Too many definitions? Journal of Chemical Education,
Volume 88, Number 3, pg. 279 – 281.
Talanquer, V. (2002) Minimizing misconceptions Tools for identifying patterns of reasoning. The Science
Teacher, Volume 69, Number 8, pg. 46 – 49.
Tarhan, L. & Acar, B. (2007). Problem-based learning in an eleventh grade chemistry class: ‘Factors
affecting cell potential’. Research in Science and Technological Education, Volume 25, Number 3,
pg. 351 – 369.
References
Zoller, U. (1990). Comments and criticism Students’ misunderstandings and misconceptions in college
freshman chemistry (General and organic). Journal of Research in Science Teaching, Volume 27,
Number 10, pg. 1053 – 1065.
Weblinks:
AUS-e-tute n.d. (2011). Chemistry tutorial: Oxidation and reduction. Retrieved from:
http://www.ausetute.com.au/redox.html
Bodner Research Lab (2011). Oxidation and reduction. Retrieved from:
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch9/redox.php
Clark, J. (2002). Definitions of oxidation and reduction (redox). Retrieved from:
http://www.chemguide.co.uk/inorganic/redox/definitions.html
Greenbowe, T. J. (2003). Chemistry experiment simulations, tutorials and conceptual animations for
introduction to college chemistry (aka general chemistry). Retrieved from:
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/animationsindex.htm
Isis Publication (2003). 10.1 – Oxidation and reduction. Retrieved from:
http://ibchem.com/IB/ibnotes/full/red_htm/10.1.htm
mtchemers (2008). Oxidation numbers. Retrieved from:
http://www.youtube.com/watch?v=EHe8-AFMsMA
mtchemers (2008). Oxidation-reduction basics. Retrieved from:
http://www.youtube.com/watch?v=e6Xxz-VBE6s
NurdRage (2010). Turn pennies to silver and gold (Chemistry trick). Retrieved from:
http://www.youtube.com/watch?v=_g_ml8tAnWE&feature=relmfu
storm808b (2011). Determining the oxidation number of elements in a compound. Retrieved from:
http://www.youtube.com/watch?v=8_CvNPuuhiM&feature=related