EDTA (lab 5) - Eldridge 2+ TA+H2Y -( aq) 2 H+ CaY(aq) + 2H...

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+ (aq) + H 2 Y 2- ( aq) CaY (aq) + 2H + (aq) 2+ (aq) + H 2 Y 2- ( aq) MgY (aq) + 2H + (aq) DTA + CaIn - + 2 H + → H 2 In - + CaEDTA Eldridge Complex-Formation Titrations with EDTA Joel I. Eldridge Abstract Water hardness is usually determined by titrating it with a standard solution ethylenediamminetetraacetic acid, EDTA. EDTA is a chelating agent used to capture metal ions. This causes the water to become softened, but the metal ions are not removed from the water. EDTA simply binds the metal ions to it very tightly. EDTA can form four or six bonds with a metal ion. For the purpose of this experiment, EDTA binds with the calcium ion in a one-to-one molar ratio. To determine the endpoint in this experiment, we used an indicator. Before the titration process the indicator imparts a pinkish tint to the solution when calcium ions are present with EDTA; the endpoint has been reach when the indicator turns blue Introduction Minerals such as Ca 2+ , Mg 2+ , Fe 3+ , SO 4 2- , and HCO 3 -  cause water to be labeled as “hard”.  Today, the determination of water hardness is useful because it provides a measure of  the quality of water for industrial, collegiate, and household uses.  At one point in time,  water hardness was defined as measure of the water to form a soap precipitate.  It has 
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Eldridge been proven that hard water is the cause of soap scum, clogged pipes and boilers.  The  binding of calcium ions with soap results in soap scum, causing an insoluble precipitate  to form the scum that is observant to the eye.  Early researched discovered that soap  softens hard water by removing calcium ions from the water.  Occasionally, temporary  hardness is caused by the bicarbonate ion, HCO 3 - , being present.   This type of  hardness can be removed by boiling water to expel CO 2 , as indicated by the following  equation:  Permanent hardness is due to the presence of the ions Ca 2+ , Mg +2
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This note was uploaded on 04/18/2011 for the course CHEMISTRY 210 taught by Professor Dr.han during the Spring '11 term at Fayetteville State University.

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EDTA (lab 5) - Eldridge 2+ TA+H2Y -( aq) 2 H+ CaY(aq) + 2H...

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