chem 1A disc acid analysis

chem 1A disc acid analysis - indicator was added to the...

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Janice Oldham Chem Lab W-1pm Dennis 7 December 2007 Discussion: Acid Analysis The standardization of NaOH was already completed for this lab so we did not complete part 1. In part 2 of the lab, we titrated vinegar with NaOH in order to determine the percent of acetic acid present in vinegar. We found this value to be around 3 percent in all three trials. We determined the number of moles of NaOH that were titrated and used stoichiometry to find the number of moles of CH3COOH. We used phenolphthalein as the indicator and titrated NaOH into the vinegar until the equivalence point was reached. The net ionic equation for this reaction is H + + OH - H 2 0 and the equilibrium constant expression is K= [NaC 2 H 3 O 2 ] [NaOH][ HC 2 H 3 O 2 ] In part 3 of this experiment we determined the mass, the number of moles, and the percent composition of the active ingredient in an antacid tablet. The tablets were dissolved in HCl, or stomach acid, due to the fact they are relatively insoluble in water. The thymol blue
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Unformatted text preview: indicator was added to the solution and it was then titrated with NaOH until an equivalence point was reached. Because NaOH only reacts with the excess of HCl, the number of moles of NaOH is equal to the excess moles of HCl that did not react with the base in the antacid. We found the percent composition of CaCO3, the active ingredient, to be around 40 percent for both antacid tablets. The balanced net ionic equation for this reaction is H + + OH- H 2 0 and the equilibrium constant expression is K= [CO 2 ][CaCl 2 ] [HCl][CaCO 3 ] Some possible sources of error in this experiment could be the molarity in both part 2 and part 3. In part 2, if the concentration of NaOH was incorrect, this would affect the percent of acetic acid in the vinegar. In part 3, if the antacid tablet did not completely dissolve in the HCl causing the neutralization capacity to be lower than it actually is.\...
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This note was uploaded on 04/02/2008 for the course CHEM 1A taught by Professor Van koppen during the Fall '07 term at UCSB.

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chem 1A disc acid analysis - indicator was added to the...

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