2CLabManual201303

For our analysis we will use disodium edta to bind to

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Unformatted text preview: the free mercury ions, effectively removing them and not allowing them to bind to enzymes and cytochromes. Thus the poison is removed and passes innocuously through the physiological system. For our analysis, we will use disodium EDTA to bind to calcium and magnesium ion as is shown below: 2 OH- + Ca2+ + H2EDTA2- 2 OH- + Mg2+ + H2EDTA2- CaEDTA2- + 2 H2O K = 5.0 x 1010 MgEDTA2- + 2 H2O K = 5.0 x 108 However, we need something to indicate when the reaction is complete. We need an indicator. The indicator will need to be another ligand and it must have a different color when it is free than when bound to a metal ion. One such ligand is Calmagite that binds to alkaline earth metals producing a color change as follows: M2+ + In2- (blue) MIn (red or pink) 23 K = ~ 7 x 10-9 The reaction of EDTA with metals (K~108) is greater than that of Calmagite (K~10-9). Thus, if a small amount of indicator is added to a solution of magnesium and calcium, a red or pink colored complex will result. If EDTA is then added via a buret, the color will change when the metal is stripped from the Calmagite and binds to the EDTA;...
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This note was uploaded on 04/09/2013 for the course CHE CHE 2C taught by Professor Nasiri during the Spring '07 term at UC Davis.

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