The formal lab reports should use the format given below.

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1 Lab Reports - First Four Experiments General comments on the lab reports. You will do formal lab reports for the first four experiments (lattice energy of argon, chain length in polyvinyl alcohol polymer, bromination of acetone, and mutarotation of glucose). There is a sample lab report in the lab textbook that you can use as a guide, and also a sample lab report posted on my website ( Be sure to list all of your lab partners on the front page of the lab report. Formal lab reports. The formal lab reports should use the format given below. 1) Abstract - A summary of the results from your experiment. This should be brief, and focus on the main results and conclusions for the experiment. Details of your work belong in other sections of the report. 2) Introduction - This should be a general discussion of the purpose of the experiment and background information concerning the theory behind the experiment. This should be relatively brief (a few pages). Try not to simply regurgitate the information in the lab manual, but put it in your own words. You can of course refer to the lab manual or lecture textbook and cite it as a reference. 3) Experimental method - This will usually be a very short section. If you follow the procedure in the lab manual all you really have to say is something like the following. "The experimental procedure used in this experiment is that given by Garland et al. [1]." where [1] is a reference to the relevant section of the lab manual or to the handout for the experiment. If you do things differently than what is given in the lab manual or handout this should be included. 4) Results - You should begin with your raw data and end with your final results. You should show step by step how you go from the experimental results to the values for the things you are finding in the experiment. Sample calculations are often useful in explaining how the data analysis was done. Tables and figures, particularly when well organized, are also often of use here. 5) Discussion - Here you do several things. You discuss the significance of your results. What do they mean? Are they consistent or inconsistent with what theory or with literature values (when those are available). You should also expand on your discussion of error in this section of the report. Your results section should have estimates of experimental error, usually based on scatter in the data. In the discussion section you

2 should think about what the main sources of error in the experiment are and try to estimate their approximate magnitude. Are the expected errors about the same size as the errors actually observed? If not, why not? 6) References - This should be a list of references used in the body of the report. This will likely include the lab manual. It may include Atkins if you use that as a source for the discussion of the experiment in the introduction. It should also include the source(s) for any literature values you use. 7) Appendix You may have an appendix containing the raw data from your experiment. You occasionally might want to include an additional appendix with other useful information. Experiments - In this section I am pointing out a few important things about each experiment. This is not meant to be an exhaustive list of things to do in the report, but a guide to some of the things that you should think about or that should be there. It will also mention those things in the lab manual you can ignore. Lattice energy of argon. (textbook) 1) The main thing you are determining experimentally is H sub, the enthalpy of sublimation of argon. You can do this from a plot of ln p vs 1/T, where p is the vapor pressure of argon and T is the absolute temperature (in K), obtained from your measurements of the vapor pressure of liquid nitrogen in the apparatus and eq. 12b. Note that equation 12b is in terms of log (that is log10) and not ln. You may check to make sure that you are using eq. 12b correctly by inserting one of the pressures from Table 3 into the equation and seeing if you obtain the corresponding table value for temperature. 2) You can find the enthalpy of sublimation using eq. 13, which is really the following equation ln p = - ( H sub/r) (1/T) + C, where R, the gas constant, is in energy units (J/mol. K) and C is a constant. By plotting ln p vs 1/T you should be able to find the value for H sub, and also the 95% confidence limits on that value. This error will of course propagate when you calculate the lattice energy for argon (eq. 8). 3) Compare your value for lattice energy to that calculated from eq. 11, which applies for a face-centered cubic lattice, the expected crystal structure. In this equation N0 is Avogadro s number. A value for can be found from the information in the book (eq. 10) and a value for is given in the book (eq. 10). To find d, the distance between adjacent argon atoms, use the figure on the next page.

3 In the above figure, the length of the unit cell, is equal to 5.30 A (or nm). d, the distance between the centers of adjacent argon atoms, can then be found by geometry. Comment on the agreement (or lack of agreement) between your experimental and calculated value for lattice energy. 4) You can ignore all of the discussion of "second law" and "third law" corrections for H sub, as your data is unlikely to be sufficiently precise to justify these calculations. We are going to assume your experimental value for the enthalpy of sublimation is, to within experimental error, the same as H sub. 5) There are literature values for H sub, though they are difficult to find. The following reference can be found online through the FIU library website. Ferreira, A. G. M. and L. Q. Lobo, Journal of Chemical Thermodynamics 40 (2008) Their value for the enthalpy of sublimation is reported in Table 5 of the paper. Use the values given on the right side of the table (for T = Ttpt). They also report two additional literature values, which you can also use in your report. Viscosity of polyvinyl alcohol solutions. (textbook) 1) Because the polymer is difficult to dissolve, I recommend that you use approximately 3.0 g of polymer to prepare your stock solution, and not g, as suggested in the textbook. 2) The book suggests preparing a third solution with concentration equal to 1/4 th of the initial concentration. DO NOT DO THIS. Because the elapsed time for this solution for the cleaved polymer will be close to that for pure water, any small errors in

4 this measurement will bias your data for the cleaved polymer. It is better to simply do the two solutions that are required (initial and 1 /2 initial). 3) It is important to use the same volume of solution in each measurement of viscosity. For the viscometers we have in the lab, a ml sample should be used (delivered by volumetric pipette). 4) Be sure to rinse out all glassware containing uncleaved or cleaved polymer solution immediately after use, particularly the viscometer. If polymer deposits out of solution it is extremely difficult to remove. For the viscometer, you should flush the narrow diameter tube of the viscometer several times with deionized water, by using a pipette bulb to suction water through the tube. After the experiment is complete, again rinse the viscometer several times with deionized water, with a last rinse using acetone. 5) In the calculations section of the lab manual values for the viscosity and density of water are given at 23 C, 25 C, and 27 C. Additional values for the viscosity and density of water are given below, and can be used if the temperature used in your experiments falls outside of the range in the lab manual. T ( C) (cp) (g/cm 3 ) You may interpolate to find the appropriate value for viscosity and density to use in finding the apparatus constant B for your viscometer (eq. 3). 6) The explanation of the calculations for this experiment is complicated, and so I have given a simplified step by step procedure for the calculations below. then a) Use eq 3 from the textbook to find B, the viscometer constant. Since ( / ) = Bt B = ( / t) Values for and for water are given above (interpolate between values if your temperature lies between two temperatures in the table). t is the average elapsed time for your measurements for water. The units for B are cp. cm 3 /g. s, where cp = centipoise.

5 b) Find the specific viscosity ( sp) for each of your four experimental solutions. Specific viscosity is given by the relationship sp = ( / 0) - 1 where is the viscosity of the solution (found from the elapsed time and eq. 3) and 0 is the viscosity of pure water. Both and 0 have units of cp, while sp is unitless. c) Find the intrinsic viscosity, [ ], in the following two ways (see eq. 4 of the textbook) - by plotting (1/c) ln( / 0) vs c, and extrapolating to c = 0. - by plotting [ ( / 0) - 1 ] vs c, and extrapolating to c = 0. In both plots the y-intercept is equal to [ ], the intrinsic viscosity. Your value for [ ] should be in the range 0.4 to 2.0. Both of the above methods should give similar values for [ ]. As a check, the experimental values for [ ] usually fall within the range 0.4 to 2.0. If your value falls outside this range check with me. Use the value for [ ] obtained by the first method (plot of (1/c) ln( / 0) vs c) in the remaining calculations. d) In your calculations of average molecular mass, the value of [ ], the intrinsic viscosity, is as found in step c above. You may then find Mv (volume average moleular mass) from eq. 7 of the textbook Mv = 7.6 x 10 4 [ ] 1.32 Convert this value into a value for Mn (number average molecular mass) using eq. 11 of the text. e) You are determining two things in this experiment in this experiment - the average molecular mass of your polymer before cleavage and the average molecular mass after cleavage. By knowing these numbers, there are several additional things you will be able to find, including - the average number of monomers per polymer, both before and after cleavage - the average number of places per polymer molecule where cleavage occurs - the number of reverse linkages (and therefore the percentage of reverse linkages) per polymer molecule. You are able to find the number and percent of reverse linkages per polymer molecule because cleavage only occurs at the site of a reverse linkage. Do all of your calculations using Mn (number average molecular mass).

6 7) Because of the small amount of data obtained in this experiment, your error discussion in this report will be less rigorous than in the other lab reports. You should, however, still give a discussion of sources of random and systematic error. 8) Since the values for average molecular mass for the uncleaved and cleaved polymer are unique to this particular batch of polymer, there are no literature values to compare to. 9) You do not have to answer the questions given in the discussion section of the lab manual. Bromination of acetone (handout). 1) You can obtain values for da/dt from the plots of absorbance vs time. You can then use Beer s law to convert this to d[br2]/dt, from which the rate of the reaction is obtained. Explain how you find da/dt and how you convert this to d[br2]/dt in the lab report. 2) You should use your data to not only find values for p and q (reaction orders) but the 95% confidence limits for those values. Your values for p and q should be rounded off to the nearest integer values before you find values for k (rate constant) from your experimental data. 3) You should report both the average value for k and the 95% confidence limits on the value for k, in appropriate units. You may express time in either seconds or minutes, whichever is most convenient. 4) You do not have to compare your results for p, q, and k with literature values, as it is difficult to find values for these in the literature (because this reaction was first investigated nearly a century ago!). Glucose (handout). 1) Remember to save the four solutions used in your measurements for optical rotation so that the equilibrium ( infinite time ) rotations can be obtained. I will measure these for you at least 12 hours after the end of the lab, which is sufficient time for the system to come to equilibrium. A file of these rotations will be kept on my website and periodically updated. 2) If you used 60% perchloric acid instead of 70% perchloric acid you need to take that into account in calculating the concentration of H + ion. Perchloric acid is a strong acid, so the concentration of hydrogen ion is the same as the concentration of perchloric acid.

7 3) Since the observed rotation is proportional to the specific rotation in the experiment (eq. 1) you can use eq. 8, with the observed rotations, to find the value for kobsd, the observed rate constant for the mutarotation reaction. It is most convenient to do the calculations in eq. 8 on a spreadsheet (such as with EXCEL), although you are free to do them by hand if you wish. 4) Although it is possible to do so, you are not required to find 95% confidence limits for the individual values of kobsd in this experiment. You are also not required to find individual values for k1 and k-1 (the forward and reverse rate constants), though this is again possible using the data you obtain in this experiment. 5) You are required to find experimental values for K, the equilibrium constant, for each of your experimental trials. You should explain in your lab report how this is done. You can average your four values to find the best value and 95% confidence limits. 6) Once you have obtained values for kobsd, you will want to discuss how this observed rate constant depends on hydrogen ion concentration. You can do this by using eq. 9 of the handout to find values for kn (neutral reaction) and ka (acid catalyzed reaction). You should discuss in the report how you do this, and also obtain correct units and 95% confidence limits for kn and ka. 7) Since finding a literature value for this reaction is difficult you are not required to compare your results to the literature.