Formal lab 4 - The Gravimetric Determination of Sulfate CHE...

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The Gravimetric Determination of Sulfate CHE 120-03 April 14, 2008
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Purpose This is a two-week experiment that will involve the quantitative determination of sulfate in an unknown and then the statistical treatment of the results obtained individually and by the entire lab section. In the first part of the experiment you will use an analytical technique known as gravimetric analysis to quantitatively determine the amount of sulfate ion SO4, present in an unknown sample. In order to achieve this goal, a technique called digestion will be introduced and the principles of stoichiometry will be used to calculate the percentage of sulfate present in the unknown. In the second part of this experiment you will apply standard statistical methods to your own results and to those of the entire lab section. Introduction There are two major parts to this lab that both have important significance to the results of the experiment. The first part of this lab is gravimetric analysis. This technique is used to quantitatively determine the amount of chemical in the unknown solution (201). Results for this genre of measurement are generally expressed in terms of percentage of a solution. Gravimetric determination is determined by precipitating the unknown as an insoluble and then weighing the dried precipitate. To attain a good sample one must dry the precipitate to remove the excess water retained from the atmosphere. Samples must then be mixed with deionized water to form an aqueous solution. A reagent must be added to the solution in order to make it precipitate. After this occurs then digestion, isolation, washing, and drying the precipitate must then occur. After all of these steps have been completed the mathematical calculations for results can be preformed. This experiment will determine the amount of sulfate ion SO4 in a BaSO4 solution. Ba + SO4 = BaSO4. After the precipitate has dried it can then be weighed and the percentage of SO4 can be attained. The calculation for the percentage is expressed by (mass of sulfate) = (mass of BaSO4)(molar mass of SO4/molar mass of BaSO4). % Sulfate is calculated by (mass of SO4/mass of sample)(100). The second part of this experiment is to use common statistical methods for the treatment of experimental data. The main focus in this section revolves around error and the propagation statistical usage of error in the experiment. Errors can be systematic or random. A systematic error is one that is at fault of the person performing the experiment. A random error is an error that happens uncontrollably. For every measurement in any experiment there will be levels of error that differ for each measuring device. These are called significant figures.
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The last significant figure for any measuring device is to be estimated. “Digits that
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Formal lab 4 - The Gravimetric Determination of Sulfate CHE...

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