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Delaney Chem162_FractCryst_Report_012812

# Calculate the molarity of fe2 from the absorbance

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Calculate the molarity of Fe2+ from the absorbance (pathlength = 1 cm) Calculate the moles of Fe2+ (moles of Fe2+= moles of (NH4)2Fe(SO4)2.6H2O) Calculate the molar mass (NH4)2Fe(SO4)2.6H2O) Calculate grams of (NH4)2Fe(SO4)2.6H2O in the crystals Mass KNO3 crystals analyzed for purity (from Step A.11.) Calculate % mass of (NH4)2Fe(SO4)2.6H2O in the crystals Absorbance of the Fe(phen)3 2+ complex at 510 nm Molar Absorptivity of fer oin, ε M-1cm-1 Calculate the molarity of Fe2+ from the absorbance (pathlength = 1 cm) Calculate the moles of Fe2+ (moles of Fe2+= moles of (NH4)2Fe(SO4)2.6H2O) Calculate the molar mass (NH4)2Fe(SO4)2.6H2O) Calculate grams of (NH4)2Fe(SO4)2.6H2O in the crystals Mass KNO3 crystals analyzed for purity (from Step B.8.) Calculate % mass of (NH4)2Fe(SO4)2.6H2O in the crystals Crystal ization Number Summary: % Mass KNO3 Recovered in Crystal ization Steps Crystal ization Number Mass KNO3 Crystal ized % of Original KNO3 Mass Grams H2O used Molar Mass KNO3 Grams KNO3 Cryst. Temp, oC Solubility gKNO3/100 g water Molality KNO3 Ksp (Based on molality) Ho Sol So Soln Chem 162 Experiment #4 I. Fractional Crystal ization of KNO3 with (NH4)2Fe(SO4)2.6H2O Impurity I . The Solubility Curve of KNO3 DATA, CALCULATIONS AND GRAPHS Part I: Fractional Crystal ization of KNO3 with (NH4)2Fe(SO4)2.6H2O Impurity Does the absorbance exceed the desired range (0 to 2.0 A)? ___yes_________ If so, what dilution factor did you use in order to get the absorbance in the desired range? _______1:10______ I . Determining the Solubility Curve of KNO3 Results and Discussion 1. Do your results indicate that fractional crystal ization works? Why or why not? My results indicate that fractional crystal ization does work. Our percent impurity decreased from 1 .38% to 2.06% to 0.58%%. This trend shows that with each crystal ization, the percent impurity decreases. Therefore, fractional crystal ization works as a means to remove impurities from a solution. 2. What is the disadvantage of fractional crystal ization? The disadvantage of fractional crystal ization is that with each crystal ization and the riddance of impurities, the percent of the final product wil decrease as wel . This is because not every KNO3 molecule wil crystal ize, therefore loosing more and more produc each time. Also, no mat er what, the final product wil be impure, there is now ay to achieve an entirely pure compound, not to mention this process takes a very long time. 3. The Handbook of Chemistry and Physics list the enthalpy of solution of KNO3 as 34.89 kJ/mole. How does your value compare? Calculate the % er or and discuss. abs(50.4kJ/mol-34.89kJ/mol)/34.89kJ/mol x 100% = 44.45%
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