lab 7 - Rob Woods Wednesday 5:10 Lab 7 Analysis of Cereal...

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Rob Woods Desk #4 Wednesday 5:10 Lab 7: Analysis of Cereal Introduction: For purpose of this experiment was to analyze the amount of iron in one serving size of Total cereal and also in one iron tablet. The cereal contains 100% of the RDA and the iron tablet has 361% of the RDA. In order for this to happen, the absorbance of iron was measured to make a calibration curve that was later used to determine the mass of iron in both the cereal and the iron tablet. Iron was extracted from the cereal and iron tablet separately and these two iron samples were placed in a spectrophotometer to measure their respective absorbencies. The molar concentration of ion was determined by the equation for the calibration curve. Once the concentration for both the cereal iron extraction and the iron tablet extraction was calculated, stoichiometry could be used to find the milligrams of iron in each substance. Experimental: Calibration Curve First, a 100 mL solution of 1.0 x 10 -3 M Fe(NO 3 ) 3 and another 100 mL solution of 0.10 M KCSN, both in 1 M HNO 3 , needed to be prepared. To prepare 1 L of 1 M HNO 3 , the .2 L of 5 M HNO 3 was diluted with deionized water until 1 L of solution was obtained. Then .0423 grams of Fe(NO 3 ) 3 was used for the Fe(NO 3 .) 3 and for the KCSN solution, .95 grams of KCSN was used. Each of these were prepared using volumetric glassware. Using a volumetric pipet, 1.00 mL of the Fe(NO 3 ) 3 was added to the 100 mL solution of KCSN. The spectrophotometer had to be zeroed using 1.0 M HNO 3 . This was completed by first filling a clean cuvette with the 1.0 M HNO 3 , then by placing it in
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the spectrophotometer and the finally by hitting the re-zero button. The solution of KCSN and Fe(NO 3 ) 3 was poured into the cuvette and placed into the spectrophotometer. Then the absorbency of this solution was recorded. The solution was later poured back into the original beaker to maintain the same volume. 10 mL of the Fe(NO 3 ) 3 was next added to the KCSN solution 1 mL at a time. The absorbency was recorded after each addition. This information was then used to make a calibration curve. The concentration of the solution on the x-axis and the absorbency of the solution on the y-axis. Cereal Extraction On a top loading balance, 32.0 grams of Total Cereal was measured out into a 600 mL beaker. The cereal pieces were then put into a plastic zip-lock bag and crushed until the cereal was well grounded up into tiny pieces. Then 30.0 grams of the cereal was weighed out and was put in a 600 mL beaker. 250 mL of deionized water was added to the beaker along with a Teflon magnet. The beaker was then placed on a stirring plate for
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This note was uploaded on 11/16/2010 for the course CHEM 104a taught by Professor Mcmillen during the Fall '07 term at Vanderbilt.

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lab 7 - Rob Woods Wednesday 5:10 Lab 7 Analysis of Cereal...

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