2CLabManual201303

Then you will measure the absorption of an unknown

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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 green complex. 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: Cl NH2 NH2 H2N H2 N N H2 Co H2 N Co N H2 N H2 OH2 Cl Cl H2 N H2 N Co NH2 OH2 N 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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