CHEM Lab Section Number: Name (printed): Signature: This exam consists of 36 questions all of equal value for a total of 225 points. Make sure that your test has all of the pages. Please read each problem carefully. There are no intentionally misleading questions; each problem should be taken at its face value. Please mark your answers on the Scantron sheet provided to you and on the actual exam. You will be given a periodic table and an exam information sheet to use during the exam. You may remove it from the exam make it more accessible. You may also use the designated Casio fx-300ms-plus calculator or equivalent non-programmable non-graphing scientific calculator during the exam. Use the back pages of the test as scratch paper. You are not allowed to use any devices capable of accessing the internet, textbooks, notes, or homemade reference sheets during the exam. You may leave if you finish the exam early. Give the exam and the information sheet to your TA and leave quietly without disturbing other students. Before leaving, check that all your answers have been properly entered on the Scantron sheet and the exam and that your name is written on every page of the exam and on the Scantron sheet. All cell phones and electronic devices must be turned off and put away. Please remove all hats and caps. Place your books and all papers out of sight under your seat. If the TA believes that you might be looking at your neighbor s paper, you will be asked to move to a new location. Exam scores will be posted on Blackboard as soon as the grading is complete. Your test will be returned to you in the first lab meeting of next week. If you have any questions regarding the grading of your exam, please notify your TA. The time available for the exam is 120 minutes. Good luck! 1 of 9
Name: Lab Section #: Please mark your answers on the scantron sheet using a #2 pencil and also mark your answers on the exam itself. Mark Test From A on your scantron. 1. Arrange the following bonds in order of increasing bond strength. (a) C I < C Br < C Cl < C F (b) C F < C Cl < C Br < C I (c) C Br < C I < C Cl < C F (d) C I < C Br < C F< C Cl (e) None of the above orders is correct. 2. Which of the following is the most electronegative? (a) Na (b) Ru (c) Si (d) Te (e) S 3. Arrange aluminum, boron, nitrogen and phosphorus in order of increasing electronegativity. (a) Al < B < P < N (b) B < Al < N < P (c) Al < N < P <B (d) N < P < B < Al (e) None of the above orders is correct. 4. Arrange oxygen, sulfur, calcium, rubidium, and potassium in order of decreasing electronegativity. (a) O > S > Ca > Rb > K (b) O > S > Ca > K > Rb (c) O > S > Rb > K > Ca (d) O > S > Rb > Ca > K (e) None of the above orders is correct. 5. Which of the following displays the greatest ionic character in its bonds? (a) NO2 (b) CO2 (c) H2O (d) HF (e) NH3 2 of 9
6. Which of the following contains covalent bonds? (a) MgF2 (b) NaCl (c) IBr (d) LiBr (e) Cu 7. Select the compound with the highest lattice energy (a) BaO (b) NaI (c) LiBr (d) MgO (e) CaS 8. The lattice energy of MgCl2 is the energy change for which one of the following processes? (a) MgCl2(s) Mg(s) + Cl2(g) (b) MgCl2(s) Mg(g) + 2Cl(g) (c) MgCl2(g) Mg 2+ (s) + 2Cl (g) (d) MgCl2(s) Mg 2+ (g) + 2Cl (g) (e) MgCl2(aq) MgCl2(s) 9. The formal charges on Cl and O in the structure shown for the ClO- ion are, respectively: (a) 0 and -1 (b) -1 and 0 (c) 1 and -2 (d) -2 and 1 (e) None of the above 10. Select the correct Lewis structure for NOCl. (a) (b) (c) (d) (e) None of these are correct. 3 of 9
CHEM 200/202 Fall 2016 Exam 3-A November, 19 2016 11. How many electron pairs are shared between the carbon atoms in C2H4? (a) 0 (b) 1 (c) 2 (d) 3 (e) 4 12. In which of the following molecules are all the bonds single? (a) O3 (b) POCl3 (c) CO (d) COCl2 (e) N2H4 13. How many resonance structures are possible for NO3? (a) 1 (b) 2 (c) 3 (d) 4 (e) 5 14. In the following Lewis structure for phosphate, phosphorus has a formal charge of and an oxidation number of. (a) 0, -3 (b) 0, 5 (c) 5, -3 (d) 5, 5 (e) 3, 5 15. In which one of the following species is the central atom (the first atom in the formula) likely to violate the octet rule? (a) BF4 (b) XeO3 (c) SiCl4 (d) NH3 (e) CH2Cl2 4 of 9
16. What is the molecular structure of the thiocyanate anion, SCN, as predicted by the VSEPR theory? (Carbon is the central atom.) (a) linear (b) bent (c) trigonal planar (d) square planar (e) none of the above 17. What is the molecular structure around the carbons in CCl2CH2 as predicted by the VSEPR theory? (a) linear (b) tetrahedral (c) trigonal planar (d) trigonal pyramidal (e) none of the above 18. What is the molecular structure of NH2Cl as predicted by the VSEPR theory? (a) trigonal planar (b) tetrahedral (c) T-shaped (d) trigonal pyramidal (e) see-saw 19. Which of the following bonds is the shortest? (a) C N (b) C O (c) C C (d) C Si (e) C S 20. Of the figures below, which does not represent the formation of a sigma (σ) bond? (a) (b) (c) (d) (e) None, they all represent sigma bonds. 5 of 9
21. How many sigma (σ) and pi (π) bonds are there in a carbonate anion? (a) 1 σ and 2 π (b) 2 σ and 1 π (c) 3 σ and no πac (d) 3 σ and 1 π (e) 3 σ and 2 π 22. Of the bonds listed below, which is the weakest? (a) A sigma (σ) bond (b) A pi (π) bond (c) A single bond (d) A double bond (e) A triple bond Consider the structure of the molecule to the right in answering the next three (3) questions: 23. In the molecule depicted, how many sigma (σ) and pi (π) bonds are present? (a) 10 σ and 4 π (b) 12 σ and 2 π (c) 14 σ and 2 π (d) 9 σ and 2 π (e) 10 σ and 1 π 24. What is the hybridization of the oxygen atom on the molecule? (a) It is not hybridized (b) sp (c) sp 2 (d) sp 3 (e) sp 3 d 25. How many carbons on the molecule have trigonal planar molecular structure? (a) 1 (b) 2 (c) 3 (d) 4 (e) 5 26. Below, each molecular geometry is paired with a possible hybridization. Which one is incorrectly paired? 6 of 9
CHEM 200/202 Fall 2016 Exam 3-A November, 19 2016 (a) T-shaped - sp 3 (b) Linear - sp (c) Square planar - sp 3 d 2 (d) trigonal planar - sp 2 (e) bent - sp 3 27. The hybridization diagram (right) depicts the carbon atom of one of the molecules listed below. Identify the correct molecule. (a) CO2 (b) CH4 (c) NCO (d) CH2O (e) CFCl3 For the following three (3) questions, use the molecular orbital diagrams below to aid in obtaining your answers. 28. Using the appropriate molecular orbital diagram, for a molecule of BN determine the resulting bond order for the ion. (a) 0.5 (b) 1 (c) 1.5 (d) 2 (e) 2.5 7 of 9
29. Which of the following diatomic molecules has the greatest number of electrons in antibonding molecular orbitals? (a) CN (b) O2 2 (c) F2 + (d) BN + (e) N2 30. From the diatomic molecules below, identify ALL those that are diamagnetic. There is more than one diamagnetic molecule, all diamagnetic molecules need to be identified in order to get the correct answer. (a) O2 (b) F2 (c) C2 (d) N2 (e) B2 31. When considering a container which holds a gas, and the ideal gas law, which of these statements is incorrect? (a) When all other factors are held constant, the pressure is directly proportional to the temperature of the gas. (b) When all other factors are held constant, the volume is inversely proportional to the number of moles of gas. (c) When all other factors are held constant, the temperature is directly proportional to the volume of the gas. (d) When all other factors are held constant, pressure is inversely proportional to the volume of the gas. (e) When all other factors are held constant, the temperature is inversely proportional to the number of moles of gas. 32. A balloon filled with 3.72 moles of nitrogen gas has a pressure of 1.42 atm at 23.5 C. The balloon expands as the temperature of the gas inside the balloon increases to 47.0 C. If the final pressure of the gas inside the balloon is 1.52 atm, what is the volume of the balloon? (a) 63.8 L (b) 0.500 L (c) 128 L (d) 64.3L (e) 87.3 L 33. A 3.50 gram mass of a pure solid is placed into an empty, sealed, 675 ml container, and it is heated until it becomes a gas. Once it has become a gas, at 249 C, the pressure inside the container is 8.23 atm. What is the molecular mass of the solid? (a) 27.0 g/mol (b) 14.2 g/mol (c) 0.0370 g/mol 8 of 9
(d) 32.4 g/mol (e) 19.3 g/mol 34. What is the density (in g/l) of nitrogen gas (N2) when the gas has been pumped into a 50.0 L balloon at 23.8 C, and it has a pressure of 1.71 atm? (a) 2.50 g/l (b) 1.33 g/l (c) 7.02 g/l (d) 1.97 g/l (e) 1.03 g/l 35. A 4.91 L cylinder has been filled with 25.0 grams of argon gas, 1.97 moles of neon gas, and 0.723 moles of xenon gas. What is the pressure inside the cylinder when it is at 32.1 C? (a) 13.7 atm (b) 21.9 atm (c) 85.7 atm (d) 18.3 atm (e) 16.7 atm 36. A solid sample of calcium carbonate is dissolved with hydrochloric acid (see unbalanced reaction below). The carbon dioxide produced from the reaction is all collected in a 2.50 L cylinder, at 25.0 C. If the reaction is performed with 23.07 g of CaCO3 and 175 ml or 2.40 M HCl, what will be the pressure of the CO2 in the cylinder? CaCO3(s) + HCl(aq) CaCl2(aq) + H2O(l) + CO2(g) (a) 4.62 atm (b) 2.06 atm (c) 2.25 atm (d) 0.388 atm (e) 1.00 atm 9 of 9