Unformatted text preview: A solid or gas will form, or a color
change will occur. This indicates that the unfilled orbitals in the oxidizing agent are at lower energy than the filled
orbitals of the reducing agent. The reaction is the result of electron transfer. If no such change is observed, no
reaction has occurred. You will test three oxidizing agents, Cu2+, Mg2+ and MnO4-, to determine their
www.webassig n.net/ebooks/wsug encheml1/lab_13/manual.html 2/10 4/15/13 Lab 13 - Redox Reactions relative reactivities. The solutions that will supply these ions are Cu(NO3)2, Mg(NO3)2 and KMnO4,
respectively. The reduction half- reaction for each oxidizing agent is shown below in alphabetical order.
Cu2+(aq) + 2 e− Cu(s)
Mg2+(aq) + 2 e− Mg(s) (9)
MnO4−(aq) + 8 H+(aq) + 5 e− Mn2+(aq) + 4 H2O(l) You will react each of them with two compounds that may act as reducing agents, hydrogen peroxide (H2O2)
and potassium iodide (KI).
You will then test three reducing agents, Cu(s), Mg(s) and Zn(s) to determine
their relative reactivities. The oxidation half- reaction for each reducing agent is listed below in alphabetical order.
( 10 )
Cu(s) Cu2+(aq) + 2 e−
( 11 )
( 12 )
Zn(s) Mg2+(aq) + 2 e− Zn2+(aq) + 2 e− You will react each of them with two species that may act as oxidizing agents, water (H2O) and hydronium
ion (H3O+) supplied by hydrochloric acid.
Note that the Cu2+/Cu couple and the Zn2+/Zn couple are also
examined in Part B of this experiment. Be prepared to compare the relative reactivities from Part A with your
observations from measuring cell potentials in Part B. Part B: Half-Cell Potentials
When electrons are transferred spontaneously (downhill in free energy), they can do work in an external
circuit if the half- reactions are separated into different compartments. This is how batteries work. Such devices
are called galvanic ce lls . It is also possible to set up an e le ctrolytic ce ll, in which an external voltage (energy
source) is used to drive a redox reaction in the nonspontaneous direction. Many industrial processes involve
electrolysis. An important example is the production of aluminum metal from its ore (Al2O3).
Separating halfreactions also allows one to measure the energy difference between the electrons in the donor orbitals of a...
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