Lab 10 - Titrations - Lab 10 Titr ations Contents > Lab 10...

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4/15/13 Lab 10 - Titrations 1/5 Contents > Lab 10 - Titrations Lab 10 - Titrations Purpose To determine the concentration of acetic acid in vinegar. Goals To perform an acid-base titration. To gain experience titrating carefully to a visible endpoint. To calculate the amount of analyte present from the result of a titration. Introduction Many laboratories analyze consumer products to determine accuracy in the labeling of the product. The very common and simple technique of titration is demonstrated in this experiment. A titration is an analytical procedure in which a reaction is run under carefully controlled conditions. The stoichiometric volume of one reactant of known concentration, the titrant , that is required to react with another reactant of unknown concentration, the analyte , is measured. The concentration of the analyte is determined from the concentration and volume of titrant and the stoichiometry of the reaction between them. The experimental setup is shown in Figure 1. A buret, which contains the titrant, is calibrated so the volume of solution that it delivers can be determined with high accuracy and precision. Titrant is added to the analyte until the stoichiometric volume of titrant has been added. This is called the equivalence point , at which the volume of titrant delivered by the buret is read. Usually, the volume readings are estimated to the nearest 0.01 mL. The delivery of the titrant is adjusted with the stopcock on the buret. With practice, one can dispense fractions of a drop of titrant and control the procedure well enough that replicated titrations agree within 0.10 mL. For this first lab, you will need your titrations to agree to within 0.50 mL.
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4/15/13 Lab 10 - Titrations 2/5 Figure 1: Titration Setup Often, the equivalence point is determined visually with an indicator. The indicator, which is a substance that changes color near the equivalence point, is added to the analyte solution. Since the color change is near but not exactly at the equivalence point, the point at which the color change occurs is called the endpoint . Indicators are chosen so the endpoint is very close to the equivalence point. It is important to keep a titration well mixed, so the titrant and analyte can contact each other and react rapidly. Either manual swirling of the flask or mechanical stirring can be used. You will use manual swirling in this experiment. Remember to constantly swirl in order to ensure complete mixing of the solutions. The most common type of titration is the acid-base titration. In this
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Lab 10 - Titrations - Lab 10 Titr ations Contents > Lab 10...

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