Exp. 4 - Course: Chem 221 Name: Ashay Mehta Experiment #4...

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Course: Chem 221 Name: Ashay Mehta Experiment #4 – Determination of the Hardness of Water Using EDTA Unknown Number: #402 Due Date: 10/16/09 Date Report Submitted: 10/16/09 Grade: Accuracy Presentation Total
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Determination of the Hardness of Water Using EDTA Ashay Mehta October 12 th , 2009 Objective: To successfully determine the hardness of water using titration techniques. Theory: EDTA will react with metal in a 1 to 1 ratio to form hexadente chelate. A pair of unshared electrons capable of complexing with a metal ion is contained on each of the two nitrogens and each of the carboxyl groups, thus forming six complexing groups. M +n + Y -4 MY n-4 and K f =formation constant = (MY n-4 ) / (M +n )( Y -4 ) The formation constants are pH dependent and are usually above 10 15 . By controlling the pH, it is frequently possible to use a titration to determine the concentration of the one of more metals without obtaining significant interference from the other metals in the solution. There is an unknown sample and a sample of tap water. The known only has magnesium in it. The tap water may have a variety of metals in it. MgIn - + HY 3- MgY 2- + HIn 2- Red Blue The metal-indicator complex should be 10 to 100 times less stable than the metal titrant complex. Procedure:
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Exp. 4 - Course: Chem 221 Name: Ashay Mehta Experiment #4...

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