# From the absorbance pathlength 1 cm calculate the

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from the absorbance (pathlength = 1 cm) Calculate the moles of Fe 2+ (moles of Fe 2+ = moles of (NH 4 ) 2 Fe(SO 4 ) 2 .6H 2 O) Calculate the molar mass (NH 4 ) 2 Fe(SO 4 ) 2 .6H 2 O) Calculate grams of (NH 4 ) 2 Fe(SO 4 ) 2 .6H 2 O in the crystals Mass KNO 3 crystals analyzed for purity (from Step B.8.) Calculate % mass of (NH 4 ) 2 Fe(SO 4 ) 2 .6H 2 O in the crystals Crystallization Number Summary: % Mass KNO 3 Recovered in Crystallization Steps Crystallization Number Mass KNO 3 Crystallized % of Original KNO 3 Mass Grams H 2 O used Molar Mass KNO 3 Grams KNO 3 Cryst. Temp, o C Solubility gKNO 3 /100 g water Molality KNO 3 K sp (Based on molality) H o Sol S o Soln EXPERIMENT 4: I. Fractional Crystallization of KNO 3 with (NH 4 ) 2 Fe(SO 4 ) 2 .6H 2 O Impurity II. The Solubility Curve of KNO 3 DATA, CALCULATIONS AND GRAPHS Part I: Fractional Crystallization of KNO 3 with (NH 4 ) 2 Fe(SO 4 ) 2 . 6H 2 O Impurity Does the absorbance exceed the desired range (0 to 2.0 A)? ___No_________ If so, what dilution factor did you use in order to get the absorbance in the desired range? ______N/A_______ Plot a graph of percent of (NH 4 ) 2 Fe(SO 4 ) 2 . 6H 2 O vs.number of crystallization steps (0,1,2) and place it here. Cover this instruction box so that your graph is an appropriate size. Be sure to include a title, axis labels, and use the chart type that connects the data points. Plot a graph of percent of KNO 3 recovered vs. the number of crystallization steps and place it here. Cover this instruction box so your graph is appropriately sized. Your graph should have three points with the first point being 100%. Be sure to include a title, axis labels, and use the chart type that connects the data points. II. Determining the Solubility Curve of KNO 3 Results and Discussion 1. Do your results indicate that fractional crystallization works? Why or why not? My results indicate that fractional crystalization works because of the impurity percentage. Only a fraction of the given compound resulted in crystals, thus signified through the percentage of impurity. I also know it worked because it allowed us to separate substances based on solubility. The crystals that I gathered contained more of the substance that was less soluble. 2. What is the disadvantage of fractional crystallization? The disadvantage of fractional crystalization is that it can not separate structural isomers in a given solution because they have similar physical properties. It only separates based on a thermal process. 3. The Handbook of Chemistry and Physics list the enthalpy of solution of KNO 3 as 34.89 kJ/mole. How does your value compare? Calculate the % error and discuss.
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