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Part 2: Questions 1. How does the measured boiling point of ethyl acetate compare to the literature values? Based on the comparison, what can you conclude about the purity of your ethyl acetate sample? 2. How does the measured refractive index of ethyl acetate compare to the literature values? Based on the comparison, what can you conclude about the purity of your ethyl acetate sample? 3. How does the measured melting point of trans-1,2-dibenzoylethylene compare to the literature value? Based on this comparison, what can you conclude about the purity of your trans-1,2-dibenzoylethylene sample? 4. If you were to conduct this distillation again, what would you do differently to improve your results?
5. You know that the boiling point of a given liquid is dependent on several different variables. What would happen to the boiling point of a liquid if... ...the atmospheric pressure was lowered: ...the volume of the liquid was doubled: 6. When measuring an ultra-micro boiling point, why should you wait until the stream of bubbles from the bell has ceased before recording the corresponding temperature? 7. What effect would a non-volatile solute have on the measured boiling point of a liquid?
Fractional Distillation PRE-LAB: The notebook pre-lab you turned in prior to conducting the experiment DATA AND OBSERVATIONS: Attach the carbon copy of your data and observations to the report sheet Part 1: Results 1. Unknown number: 2. What are the literature boiling points of each of the following compounds? Include your source. PUBChem cyclohexane: Bly hexane: Report Sheet: Laboratory 8 toluene: 116.640 3. Using the GC chromatograms, report the retention times of each substance in your mixture. The units of time, along the x-axis of the chromatogram, are in "min." Lower-boiling component: 1.63 Higher-boiling component:_ 3.05
4. What are the identities of the two substances from your unknown mixture? Lower-boiling component: Cyclohexane Higher-boiling component: toulene 5. Construct a "distillation-plot" of Temperature (°C) versus Total Volume of Distillate (mL) using Microsoft Excel and attach it to this report sheet. Be sure the graph has a title, and that both axes are labeled and that the data points should be connected by a smooth line (drawn by the program, not by hand). 6. Calculate the percentages of the two liquids in the distillate and pot material (%A, %B in distillate; %A, %B in pot). Show your calculations on each graph. Attach the GC chromatograms with peaks appropriately labeled. 7. Which material has the highest purity (indicated by the highest perecentage of a single component), the distillate or the pot? Using your data, explain why one is more pure than the other. Distate. Because when hear is added It is free of impurity pot, the pure substance vaporizes and then condensed as distillate. Bogner to the
8. You performed this fractional distillation using an air condenser as the "fractionating" column. Explain why the distillate may have been obtained in higher purity if you would have used a fractionating column packed with glass beads. 9. Define "azeotropes" and provide an example of an azeotrope. If you look up the answer to this question, reference the source.
+ Slide) Play Keynote Live Table Chart: Text Shape Media Comment Collaborate Experimental Data: • Observed ultra-micro boiling point of ethylacetate = 76 C. . . • Observed refractive index of ethylacetate (recorded at 25 C) = 1.524. 110-113 • Observed melting point of trans-1,2-dibenzoylethylene= . C
Experimental Data: Volume of distillate 0.5 ml 1.0 ml 1.5 ml 2.0 ml 2.5 ml 3.0 ml 3.5 ml 4.0 ml Temperature C 37.0 37.5 37.9 38.4 39.3 56.0 56.7 60.9