Edta Lab Report

Discuss why EDTA and Erio-Black T are good substances to use for testing the water samples in this experiment. (Hint: Consider the complexation reactions, presence of Mg2+, Kf, and color in your answer.)
EDTA is a good substance to use for testing the water samples in this experiment because it reacts will the metals to produce a one to one ratio of EDTA to metal complexes. In addition, the reaction equilibrium favors the formation of the EDTA to the metal complexes, therefore making it a good indicator for determining the presence of metal cations. Specifically, in the lab Mg2+ cations reacted with with the EDTA to form EDTA complexes. This then resulted in a change of color for the indicator. Similarly Erio-Black T is also a good substance to use for testing the water samples in this experiment because it works as an indicator and changes from red then to purple and finally to blue around the pH range of 7-11. In addition, we used a pH 10 buffer to ensure that the

Draw a picture of the ligand and circle all of the binding sites in the molecule.
EDTA is a hexadentate and chelating ligand.
(EDTA has 6 binding sites. Two of the binding sites are lone pairs binding sites on the nitrogen atoms and four of the binding site are at are at the locations of hydrogen atoms (carboxylic acid groups).)
Why was it necessary to add buffer to your water sample before performing the titration? What would happen if this step was omitted?
The buffer ensures that the reactions takes places at the proper pH. The indicator, Eriochrome T must remain at a pH of around 10 for it to work and change colors correctly. Specifically, in order for the reaction between EDTA and calcium to go to completion the water sample has to remain basic. This is acc accomplished by the presence of the buffer. If this step was omitted the indicator would not occur properly and one would not be able to see whether or not there is a presence of metal