Part III: Ammonia, NH3 1. Draw a Lewis dot structure for NHs and apply the VSEPR analysis. [What boud angles do you expe

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Part Iii Ammonia Nh3 1 Draw A Lewis Dot Structure For Nhs And Apply The Vsepr Analysis What Boud Angles Do You Expe 1 (91.85 KiB) Viewed 66 times

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Part III: Ammonia, NH3 1. Draw a Lewis dot structure for NHs and apply the VSEPR analysis. [What boud angles do you expect according the VSEPR theory? How does this compare to the angles determined by Spartan? Look up the experimental bond length in ammonia. How does this compare to the bond distance Spartan predicted? Discuss with a neighbor.] NOTE: Always draw the Lewis structure before performing a Spartan calculation or else you may not choose the optimal starting geometry. Spartan needs a fairly good guess before starting its calculations. (That's one more reason for mastering VSEPR concepts!) 2. Open a blank tab using the leftmost button at top of the screen or by selecting File>New Build. Your methane results will still be accessible from the tabs at the bottom of the screen 3. Choose the tab for the inorganic tool kit. Select the element N from the periodic table using the large button at the top. Click on the non-planar structure with 3 single bonds (as you should have predicted from your Lewis structure and VSEPR analysis). We call this structure "trigonal pyramidal" but Spartan calls it "XBentTrigonal". You can verify that you have the right button by hovering over it for a few seconds. Note that, for Spartan, this is only a starting point. The program itself will decide what the molecule's structure actually is based on the calculations it performs. 4. Click once in the middle of the large display window. An N atom with 3 bonds should appear. It will be orangish. (There is a standard color coding for elements in molecular display software.) 5. Click on the View (eyeglasses) button at the top of the screen (or select Build>View). The drawing tools will disappear and Spartan will add hydrogen atoms to each of the open bonds. 6. Save your file to one of your drives naming it iammonia".
7. Let's get Spartan to calculate the best structure for ammonia 2 Choose the dropdown menu Setup, and then choose Calculations 6. Select Equilibrium Geometry, Gas, Hartree Fock and 6-316 Revision 2019.01.20 CHM1221 (University Chemistry 1) Lab Manual Page 9 Computational Chemistry 1/2019 Lawrence Technological University Page 10 C. Click Submit d Save the molecule as "ammonia". e. Click OK f. You will see a dialog box indicating that a calculation has started, and then a second dialog box when it is complete. Clear these from the screen as they appear. 8. Spartan has calculated what it thinks is the best structure and displayed it for you. Measure the N-H bond distances by clicking on the bonds. Check all of the N-H distances. Record what you find and save to your ammonia" file. 9. Measure the H-N-H bond angles using Geometry>Measure Angle and then clicking on two bonds in succession (or three atoms, HN, H, in that order). Check all of the bond angles and record what you find. 10. Save a copy of this molecule for your lab report. Do this by selecting Save Image As.
On your own: PH Draw the Lewis structure and make your VSEPR predictions. In a new window, create the molecule PH: Do this in exactly the same way you created NHbut select the element, P and then the XBent Trigonal" button. Draw its Lewis structure. Complete steps 2-10 for PH3. Compare these results with those for NH3. [What happened to the bond lengths? What happened to the angles? Do the bond angles of the two molecules approximately conform to the predictions of VSEPR theory? Why or why not? Are the atomic orbitals of phosphorous hybridized in this molecule? Discuss this with your lab partner or neighbor.] Save and label your image as "phosphine" or "PH3"
Part III: Group 15 compounds: NH, PH3 Results for XH NH3 Ammonia PH phosphine Draw Lewis dot structures for NH3 and PH3: H-XH bond angle (Spartan) H-X-H bond angle (VSEPR) X-H bond distance (Spartan) X-H bond distance (literature)