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Unformatted text preview: mentally determine the wavelengths of the visible
absorption maxima of two non-interacting compounds and measure the molar
absorptivity for both of them at these two different wavelengths. Then, you will measure
the absorption of an unknown mixture of two compounds in order to determine the
concentration of each species.
The two compounds referred to above are the green “chloro” complex synthesized in the
last experiment and a red “aquo” derivative, which you will make from the solution of the
In acidic solutions with low free chloride ion concentrations, one of the chloride ions in
the trans-[Co(en)2Cl2]+ complex ion can be replaced by a water molecule to give an
equilibrium mixture of the cis and trans isomers of the aquo complex,
[Co(en)2(H2O)Cl]2+. This reaction is accompanied by a color change from green to red:
H2 Co H2
N Co N
H2 OH2 Cl Cl H2
N Co NH2
H2 Cl trans-[Co(en) 2Cl2]Cl + H2O H+ cis- & trans- [Co(en)2(H2O)Cl]Cl2 “chloro” complex (green color) “aquo” complex (red color) Throughout this experiment, the green-colored trans-[Co(en) 2Cl2]Cl will...
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- Spring '07