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Preparing and Analyzing a Compound

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Tare-sang Nam Chem 101 10/23/02 Lab #6 Preparing and Analyzing a Compound Part 1 Summary of Data The initial mass of BaCO3 in the vial: 21.934g The final mass of BaCO3 in the vial: 14.526g The total amount of BaCO3 transferred into the 250-ml beaker: 7.408g The mass of a piece of student grade filter paper on the large watch glass: 34.660g The mass of the BaCl2.2H2O crystals /filter paper/watch glass: 39.117g Calculations Discussion 1) The method of dissolving BaCO3 in water is not sophisticated enough to make the chemical reaction that yields barium chloride, 100%. 2) The lab manual says, "you do not want to use up the BaCO3 entirely so when the mixture doesn't fizz very much and has a small amount of solid (a good, healthy pinch) ...read more.


large watch glass: 34.660g The mass of the BaSO4/filter paper/watch glass before drying in the oven: 35.165g The mass of the BaSO4/filter paper/watch glass after drying in the oven: 35.095g The mass of the BaSO4 crystals: 0.435g Calculations and Discussion 3) The direction of the error if heavy metal cations were present in a sample is positive because these heavy metal cations are held on surfaces of barium sulfate. This process of coprecipitation adds more mass to the crystals of barium sulfate, which results in the positive error. 4) If the nitrate anions are present, it will cause the negative error because a nitrate anion is lighter than a sulfate anion. ...read more.


Conclusion Precipitations, filtrations, and evaporations were used to prepare barium chloride dihydrate from crude barium carbonate. The experimental design in part I was, however, not sophisticated enough for us to expect a high percent yield. In part II, the quantitative analysis of barium chloride dihydrate for the purity was performed. From the weight of BaSO4 obtained, the weight of pure BaCl2.2H2O in the sample. The percent purity of BaCl2.2H2O was calculated to be 98.7%. The error could have been large if heavy metal cations, which are likely to be coprecipitated with barium sulfate, were present; moreover, if the anions nitrate and chlorate were present, they could have been coprecipitated as barium salts, which result in negative and positive errors respectively. ?? ?? ?? ?? 2 3 2 3 ...read more.

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