Lab 4 Final Write Up

Lab 4 Final Write Up - 1 Martinez Blanca Martinez Chemistry...

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1 Martinez Blanca Martinez Chemistry 1A Lab October 24, 2011 John McMurry Acids in the Environment II: Indicator Titration Abstract : The purpose of this experiment was to titrate HCl to determine its concentration. The concentration of an acidic solution is a measure of the amount of solute, the acid, present in a particular solution. The experiment was conducted by using bromocresol green indicator to signal when the flask containing TRIS base, would change to a neutral pH after being titrated with HCl. Using the known volume and molar mass of TRIS, the concentration of HCl was calculated. The average molarity was 1.008E-1. Introduction : The procedure that was carried out was done using a dilute solution of HCl to titrate a basic solution containing TRIS. The gradual change in pH was measured using bromocresol green indicator. The indicator allowed the change in pH to be seen. Because the changes in the indicator color were sudden, the bromocresol was a source of error. HCl and TRIS react on a one-to-one ratio according to the following reaction: HCl (aq) + (HOCH 2 ) 3 CNH 2 Cl - (aq) + (HOCH 2 ) 3 CNH 3 + (aq). The purpose of this experiment was to simulate the way scientists determine the amount of any strong acid in a solution. This is an important process because it helps make conclusions about the state of the environment, such as how much sulfuric acid waste there is in abandoned mines. The data gathered showed that the volume of TRIS in a flask determined how much HCl solution would be needed to neutralize it. Furthermore, because TRIS and HCl are proportional, the molarity of HCl can be accurately calculated each time. This procedure was used to calculate the molarity of HCl because the moles of HCl do not change if it is in a solution. The moles of a concentrated solution are equal to those in a dilute solution. When one combines this relationship
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