CHEM 1161-01-F23-Exam 2 Form A-Solutions

CHEM 1161 Fall 2023 Exam #2A D. Matthew Page 1 of 8 CHEM 1161 Exam #2 Thursday, November 2, 2023 Name: ____________________________ Place an ‘X’ in the box for your recitation: Ben: Tina: [ ] Tu 11:45 am [ ] Tu 3:25 pm [ ] M 11:45 am [ ] M 1:35 pm [ ] Tu 1:35 pm [ ] W 3:25 pm -1 point if you fail to mark your recitation! This is a closed book/notes exam. You have 60 minutes to complete it. While you can use a calculator (graphing calculators are acceptable) on the exam, you are not allowed to use a calculator with internet access or one on your phone, computer, etc. Note that there are 6 pages with questions on them, so be sure to look at them all. For all non-multiple-choice questions, you must show all work for full credit. If you have any questions as you go through the exam, please don’t hesitate to ask. Lastly, there is a sheet of potentially useful information along with a periodic table at the end of the exam that you are welcome to tear off. Good luck!!! Problem(s) Possible Points Your Score 1-12 36 13 8 14 6 15 22 16 10 17 8 18 10 19 3 (Bonus) TOTAL 100 Form: A Sect: 01 Solutions

CHEM 1161 Fall 2023 Exam #2A D. Matthew Page 2 of 8 1. (3 Points) Which of the following molecules is the most polarizable? (Circle your answer) a. Ethane, ࠵? ଶ ࠵? ଺ b. Butane, ࠵? ସ ࠵? ଺ c. Hexane, ࠵? ଺ ࠵? ଺ d. All the above molecules are equally polarizable. 2. (3 Points) Valence bond theory is a model that describes a bond between two atoms as … (Circle your answer) a. … the two atoms being near each other. b. … the overlap of half-filled orbitals between the atoms. c. … the transfer of electrons between the atoms. d. … the sharing of electrons between the atoms. 3. (3 Points) Hydrogen bonding is best described as a form of which type of intermolecular force? (Circle your answer) a. Dipole-dipole force b. Ion-dipole force c. London dispersion force d. The bond between hydrogen and oxygen atoms within the molecule. 4. (3 Points) Which of the following quantities can be used to convert between units of volume and moles? (Circle your answer) a. Avogadro’s number b. Molar mass c. Molar ratio d. Molarity 5. (3 Points) Through elemental analysis of an unknown compound, you determine its empirical formula is ࠵?࠵? ଶ ࠵? . Given that the molar mass of the molecular formula is 90.078 ࠵?/࠵?࠵?࠵? , what is the molecular formula of this compound? (Circle your answer) a. ࠵?࠵? ଶ ࠵? b. ࠵? ଶ ࠵? ସ ࠵? ଶ c. ࠵? ଷ ࠵? ଺ ࠵? ଷ d. ࠵? ସ ࠵? ଼ ࠵? ସ O O O O O

CHEM 1161 Fall 2023 Exam #2A D. Matthew Page 4 of 8 13. (8 Points) Below is a figure that shows how the boiling point changes between hydrides of different elements. Each set of data, read left-to-right, represents replacing the central atom with the next element down that column on the periodic table. As you see, the boiling points generally increase as you replace the central atoms with heavier elements, but the first molecule in the first three data sets has a higher boiling point then the rest of the set. In a couple sentences, explain why this is. Note: Don’t just list the primary property at play here. I want you to fully explain why that property influences boiling point. 14. (6 Points) How many sigma (࠵?) and pi (࠵?) bonds are present in TNT (2,4,6- trinitrotoluene), shown below. Place your answers in the spaces provided. Sigma bonds: ________ Pi bonds: ________ H2O HF and Nitz are all capable of hydrogen bonding while all of the other molecules are not Hydrogen bonding is a stronger intermolecular force than dipole dipole and dispersion forms these are what the other molecules have and the stronger the intermolecular force the higher the boiling point y 21

CHEM 1161 Fall 2023 Exam #2A D. Matthew Page 5 of 8 15. (22 Points Total) Consider the balanced reaction below between phosphoric acid and calcium hydroxide and answer the questions that follow. 2 ࠵? ଷ ࠵?࠵? ସ (࠵?࠵?) + 3 ࠵?࠵?(࠵?࠵?) ଶ (࠵?࠵?) → ࠵?࠵? ଷ (࠵?࠵? ସ ) ଶ (࠵?࠵?) + 6 ࠵? ଶ ࠵?(ℓ) For these questions, consider 566 mL of 2.777 M phosphoric acid reacting with 432 mL of 2.035 M calcium hydroxide. a. (10 Points) What mass (in grams) of water do you expect this reaction will produce? b. (9 Points) Once the reaction has completed, what do you expect the molarity of the excess reactant to be? c. (3 Points) Which of the follow is the limiting reactant? (Circle your answer) ࠵? ଷ ࠵?࠵? ସ ࠵?࠵?(࠵?࠵?) ଶ ࠵?࠵? ଷ (࠵?࠵? ସ ) ଶ ࠵? ଶ ࠵? XS LR 566mL 2777M 432mL z.org 18 015g not 0.566243704 2.777 mot H Poy lemol H2O 18.015g H2O 1L 43104 2 mot it Poy mo H2o 84 9g H2O 0.432L Tacoma 2.035 not Cacoalz Gmo H2O 18.015g H2O 1L 410412 3 moi colon Imo H2o 31.7g 20 remaining notesHzPQ initial moles Hypo 0.5662 2 777 mot 43004 1.57 no 1 57m01 O 586m01 IL 0.986 mot moles Hs Poy consumed If j8 0.986mmol 0.432L Tacoma 2.035 not Cacottlz 2m01 1 3704 0.586 no 0.5662 0.432 IL Calontz 3 mol Calo't z 0.99 M

CHEM 1161 Fall 2023 Exam #2A D. Matthew Page 7 of 8 18. (10 Points) You setup a titration involving aqueous solutions of nitric acid, ࠵?࠵?࠵? ଷ , and barium hydroxide, ࠵?࠵?(࠵?࠵?) ଶ . How many milliliters of 0.765 ࠵? ࠵?࠵?࠵? ଷ are needed in this titration to neutralize 325 ࠵?࠵? of 1.500 ࠵? ࠵?࠵?(࠵?࠵?) ଶ ? 19. (3 Bonus Points) In your eyes, who is the better wizard between Gandalf and Dumbledore? Feel free to elaborate and/or add another to the list you feel is superior. If you don’t have an opinion, say so, and I will still give you the bonus points. 2 ANO lag Bacottlzraq I 24206 t Ba Nos lag mL 0.765M 325mL 1 500M 0.325L Balothz 1.500 mot Balottle 2m01 H NO I L HN 03 I L Ba07th I mol Bacot 0.765 mot HN 03 1.27 L T 1270 mL

CHEM 1161 Fall 2023 Exam #2A D. Matthew Page 8 of 8 Potentially Useful Constants and Conversions ࠵? ஺ = 6.022 × 10 ଶଷ ࠵?࠵?࠵? ିଵ ࠵? = 3.00 × 10 ଼ ࠵?/࠵? ℎ = 6.626 × 10 ିଷସ ࠵? ∙ ࠵? 1 ࠵?࠵?࠵? = 1.66054 × 10 ିଶ଻ ࠵?࠵? 1 ࠵?࠵? = 2.2046 ࠵?࠵? 1 ࠵? = 1.0936 ࠵?࠵? 1 ࠵?࠵? = 2.54 ࠵?࠵? (࠵?࠵?࠵?࠵?࠵?) 1 ࠵?࠵?࠵? = 4.184 ࠵? Potentially Useful Equations ࠵? = ℃ + 273.15 (࠵?࠵?࠵?࠵?࠵?) ࠵? = ࠵? ࠵? ࠵? = ℎ࠵? ࠵? = ℎ࠵? ࠵? ࠵? ௡ = −2.18 × 10 ିଵ଼ ࠵? ൬ 1 ࠵? ଶ ൰ (࠵? = 1,2,3, … )