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ChemLab113-0078 - Acceptability for the first part of this...

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Unformatted text preview: Acceptability for the first part of this experiment is based on the values of the differences betweenthe absorbances measured for the four colored solutions and the true absorbances of those solutions. There is a maximum acceptable value for each of the differences. The computer will use those values to identify faulty solutions and tell you to prepare them again. In doing so be particularly careful in pipetting the standard iron solution. We will use the following table to see how the computer handles the data fi-om the second part of the experiment. The mass and absorbence given in the table are for one of the three highly colored solutions prepared from the iron compound. Iron Solution from Compound Mass of Compound 0.0542 g Absorbance of solution from compound 0.451 The computer begins by calculating the slope of the straight line it obtained in the first part of the experiment. In the case of the data given here that slope is 0.205/ppm. The slope is used in combination with the absorbance to calculate the iron concentration in the highly colored solution prepared fiom your compound. 1 Iron concentration = 0.451(%) = 2.20 ppm The concentration is then used to calculate the mass percent iron in the compound. The calculation is a combination of the following three steps. Step 1: The mass of iron in the highly colored solution propared train your compound is calculated. The concentration of the solution (2.20 ppm) and the solution volume (28.0 ml.) are used for the purpose. 2.20 mg oftron ( 1 L ) (23.0 mL of solution) = 0.0616 mg ofFe L of solution 1000 mL Step 2: The mass of iron in the 100 mL of solution originally prepared from your compound is calculated. The key fact used in the calculation is that the mass of iron in the highly colored solution equals the mass of iron in 1.00 mL of the original solution. 0-0616 m_g °___f “on (_S_1 ) (100 mL of solution) = 0.00616 g of Fe ‘ 1.00 mL of solution 1000 m8 107 ...
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