CHEM 162 EXPERIMENT 4: I. Fractional Crystallization Of KNO3 With 2Fe2.6H2O Impurity II. The Solubility Curve Of KNO3

CHEM 162 EXPERIMENT 4: I. Fractional Crystallization Of KNO3 With 2Fe2.6H2O Impurity II. The Solubility Curve Of KNO3. Goals of this lab: • Demonstrate the purification of a solid sample using the process of fractional crystallization • Construct a solubility curve for potassium nitrate • Apply the mechanics of dimensional analysis and an understanding of solubility of solids to calculatecomposition by mass, % impurity, % recovery, solubility product constant, enthalpy of solution formand entropy of solution formation • Apply Beer's law to detect the amount of impurity in a solid sample • Assess the accuracy of experimental data (compared to a known value) and identify sources of error• Use Excel to graphically represent and interpret experimental data Your lab report will be graded on the following criteria using a poor/good/excellent rating system: • Data and results are detailed, reasonable, and complete • Calculations are complete and correct, with proper use of significant figures and units • Conclusions are reasonable and logical • Error analysis is well-supported and valid • All graphs and tables are clearly and accurately labeled; entire report is typed By signing below, you certify that you have not falsified data, that you have not plagiarized any part of tlab report, and that all calculations and responses other than the reporting of raw data are your own independent work. Failure to sign this declaration will result in 5 points being deducted from your lab sSignature: __________________Skyler______________________ This lab is worth 60 points: 10 points for notebook pages, 50 points for the lab report (Do NOT include your notebook pages when you scan your report for upload into Gradescope.) Laboratory Waste Evaluation Laboratory waste is considered anything generated during an experiment that is disposed of down the sewer draingarbage, collected in a container for disposal by the UW Environmental Health & Safety department, or released inenvironment. Based on the written lab procedure and your actions during the lab, list the identity and approximateor volume) of waste that you generated while performing this experiment. - 10 g KNO3 - 1g NH43FeSO4 Page 2 of 28 - 10 g KNO3 - 1g NH43FeSO4 - filter paper -weighing paper - ice and tap water - papertowels - sodium bicarbonate and pH strips Page 3 of 28 NAME: QUIZ SECTION: DATA, CALCULATIONS, AND GRAPHS Part I. Fractional Crystallization of KNO 3 with (NH4)2Fe(SO4)2·6H2O Impurity A. Starting Components (Fract. Crystallization #0) Step 3: Mixture before first crystallization mass KNO3 mass (NH4 )2Fe(SO4 )2 . 6H2O Total mass of the sample mixture % Impurity (i.e., % Fe compound in the mixture)* *(This is your % impurity for Fract. Crystallization # 0) Fract. Crystallization #1 Step 7: mass of dry filter paper + watch glass Step 10: mass of KNO3 crystals + filter paper + watch glass mass of KNO3 crystallized % KNO3 recovered (% of KNO3 in Step A.3.) Step 11: mass of KNO3 crystals to be analyzed for purity in Part I.C B. Fract. Crystallization # 2 (Re-crystallization) Step 5: mass of dry filter paper + watch glass Step 7: mass of KNO3 crystals + filter paper + watch glass mass of KNO3 crystallized % KNO3 recovered (% of KNO3 in Step A.3.) Step 8: mass of KNO3 crystals to be analyzed for purity in Part I.C Page 4 of 28 Page 5 of 28 NAME: QUIZ SECTION: C. Analysis to Determine % Impurity First Crystallization Step 3: Absorbance of the Fe(phen)3 2+ complex at 510 nm What is your absorbance after dilution? (if applicable) Multiply your absorbance by the dilution factor (if applicable) Molar Absorptivity of ferroin, e Calculate the molarity of Fe2+ from the absorbance (pathlength = 1 cm) Volume of ferroin complex solution prepared in Steps C.1. and C.2. 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.) (this cell will autofill) 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_______ Type your calculation for molarity of Fe2+ (1 mol ferroin = 1 mol Fe2+) A=E*I*c 1.526= 1.25 x 10^4 1/M*cm * 1 cm * C C = 1.221 x 10^-4 M Type your calculation for moles of Fe2+