Exam 3 Chem 111 Fa23 vA KEY

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1 CHEM 111 – Exam 3 Thursday, October 26, 2023 Version A Name (printed): _______________________________________ CSU ID: ______________________ For this exam, you will need a pencil, a TI-30X IIS, TI-30Xa, or a TI-36X Pro calculator (without the cover), and your CSU ID card. NO OTHER MATERIALS are allowed on your desk during the exam. Calculators may not be shared. Having a cell phone, smart watch or other electronic device on your person will be considered a violation of CSU’s Academic Integrity Policies. HONOR PLEDGE : “I have not given, received, or used any unauthorized assistance .” Signature: ________________________________________________ Choose the single best answer to each multiple-choice question. When you have finished taking the exam, the cover sheet and the answer sheet must be turned in. Make sure to include your CSU ID number and version letter on your answer sheet. You will be graded solely on the answers that you report on your answer sheet, so be sure to bubble in your exam version and answers carefully. This exam has 35 equally weighted multiple-choice questions. There are 12 pages including this page. Good luck! Conversion Factors for SI and Other Common Units Mass 1 kg = 2.205 pounds (lb); 1 lb = 0.4536 kg = 453.6 g 1 g = 0.03527 ounce (oz); 1 oz = 28.35 g Length 1 m = 1.094 yards (yd); 1 yd = 0.9144 m (exactly) 1 m = 39.37 inches (in); 1 foot (ft) = 0.3048 m (exactly) 1 in = 2.54 cm (exactly); 1 mi = 1.609 km 1 mi = 5280 ft (exactly) Volume 1 L = 0.2642 gallon (gal); 1 gal = 3.785 L 1 L = 1.057 quarts (qt); 1 qt = 0.9464 L Select Electronegativity Values: H (2.1), C (2.5), N (3.0), O (3.5), F (4.0), S (2.5), Cl (3.0), P (2.1) Electron Domain and Molecular Geometries: Linear Trigonal Planar (bent) Tetrahedral (trigonal pyramidal, bent) Trigonal Bipyramidal (seesaw, T-shaped, linear) Octahedral (square pyramidal, square planar)

2 Constants and Conversion F act ors h = 6.626 ×10 -34 J ∙ s c = 2.9979 × 10 8 m/s Avogadro’s number = 6.022 × 10 23 T (in K) = 273.15 + T (in  C) 1 mL = 1 cm 3 (exactly) The Electromagnetic Spectrum Equations d = m/V V (sphere) = 4/3  r 3 V (cube) = length  width  height 𝐸 = −2.179 × 10 −18 𝐽 ( 1 𝑛 2 )  = c E photon = h ν = ℎ? 𝜆 𝐸 ∝ 𝑞 1 𝑞 2 ? Δ𝐸 = −2.179 × 10 −18 𝐽 ( 1 𝑛 𝑓 2 − 1 𝑛 𝑖 2 )

3 You have version A of the exam. Please bubble A on your answer sheet. 1. Arrange aluminum, nitrogen, and phosphorus in order of predicted increasing electronegativity. A. N < P < Al B. P < N < Al C. Al < P < N D. P < Al < N E. None of these orders is correct. 2. A nonpolar covalent (i.e., pure covalent) bond would form between .... A. Na – Cl B. H – Cl C. Br – Br D. Li – Br E. Na – Br 3. Which of these choices is the best Lewis structure for ozone, O 3 ? A. B. C. D. E.

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4 4. What is the mass percent sodium in sodium carbonate? A. 43.4% B. 11.3% C. 45.3% D. 27.7% E. 21.7% 5. 50.00 g of a compound contains 38.87 g iron and 11.14 g oxygen. What is the empirical formula of the compound? A. Fe 2 O B. FeO C. Fe 2 O 2 D. Fe 2 O 3 E. Iron (II) oxide 6. Which of the following is a molecular formula for a compound with an empirical formula of CH 2 O and a molar mass of 150. g/mol? A. C 7 H 18 O 3 B. C 5 H 10 O 5 C. C 3 H 6 O 3 D. CH 2 O E. None of the answers is correct. 7. Which of these covalent bonds is the most polar (i.e., highest percent ionic character)? A. Al – I B. Si – I C. Al – Cl D. Si – Cl E. Si – P

5 8. The electronegativity of an element is a measure of . . . A. the ability of a bonded atom to draw shared electrons to itself. B. the amount of energy required to remove an electron from atoms. C. the amount of energy released when atoms gain an electron. D. the distance between electrons. E. the number of valence electrons. 9. How many lone pairs of electrons need to be added to complete this Lewis structure? A. 5 B. 8 C. 6 D. 1 E. 14 10. What is the formal charge of the sulfur atom in the Lewis structure below? A. 0 B. +1 C. – 1 D. +2 E. – 2 11. Consider the two possible Lewis structures for formaldehyde CH 2 O. Considering formal charges, which structure is to be preferred and why ? A. The left structure because the total of formal charges is zero B. The left structure because the total of formal charges is -1 C. The left structure because all formal charges are zero D. The right structure because the total of formal charges is +1 E. The right structure because all formal charges are zero

6 12. The number of resonance structures for the sulfur dioxide molecule that satisfy the octet rule is _____. A. 1 B. 2 C. 3 D. 4 E. none of these 13. For a molecule with resonance, is a single Lewis structure a complete description of the structure? A. No , because the actual structure of the molecule is a hybrid of the resonance structures. B. No , because the molecule jumps back and forth among all possible resonance structures. C. No , because resonance structures represent slightly different arrangements of atoms. D. Yes , because almost all molecules can be represented by whichever single resonance structure has the lowest energy. E. Yes , because resonance structures typically differ only in the position of double bonds. 14. Which of the following is the best Lewis structure for the NO radical? A. B. C. D. E. 15. Which of the following can have an expanded octet: boron, carbon, and/or phosphorus? A. boron, carbon, and phosphorus B. boron only C. carbon only D. phosphorus only E. None of these can have an expanded octet.

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7 16. NCl 3 contributes to the “chlorine smell” of swimming pools. What is the electron-domain geometry of NCl 3 ? A. trigonal planar B. tetrahedral C. trigonal pyramidal D. T-shaped E. seesaw 17. What is the molecular geometry of NCl 3 ? A. trigonal planar B. tetrahedral C. trigonal pyramidal D. T-shaped E. seesaw 18. According to VSEPR theory, how many electron domains are around each carbon atom in the plant hormone ethylene, C 2 H 4 with the Lewis structure shown below? A. 1 B. 2 C. 3 D. 4 E. 0 19. What is the ideal bond angle of the H-C-H bond in an ethylene molecule, indicated by the arrow in the Lewis structure below? A. 180˚ B. 120˚ C. 90˚ D. 109.5˚ E. 67.9˚

8 20. What is the actual bond angle around the oxygen atom in a methanol molecule (the C-O-H bond angle), with the Lewis structure shown below? A. slightly greater than 120 ˚ B. slightly less than 120˚ C. slightly greater than 109.5˚ D. slightly less than 109.5˚ E. 180˚ 21. What is the molecular geometry of sulfur hexafluoride, with the Lewis structure shown on the right? A. Trigonal bipyramidal B. Seesaw C. T-shaped D. Octahedral E. Square pyramidal 22. Which sentence best describes a CF 4 molecule (Lewis structure below)? A. CF 4 has no polar bonds, and the molecule is non polar. B. CF 4 has no polar bonds, but the molecule is polar . C. CF 4 has polar bonds, but the molecule is non polar. D. CF 4 has polar bonds, and the molecule is polar . E. CF 4 is an ionic compound. 23. Which picture best represents the molecular dipole in CHF 3 ? A. B. C. D. E.

9 24. Which kind(s) of intermolecular forces exist between dimethyl ether molecules (CH 3 OCH 3 , with the Lewis structure below)? A. Dispersion forces only B. Dipole-dipole interactions only C. Hydrogen bonding only D. Dispersion forces and dipole-dipole interactions E. Dispersion forces and hydrogen bonding 25. What type of intermolecular forces are due to the attraction between temporary dipoles and their induced temporary dipoles? A. Metallic bond B. London dispersion C. Hydrogen bond D. Ionic bond E. Covalent bond 26. What intermolecular forces exist between molecules of ethanol and acetone? A. London dispersion forces only B. London dispersion forces and ion-dipole forces C. London dispersion forces and dipole-dipole forces D. London dispersion forces, dipole-dipole forces, and hydrogen bonding E. Ion-dipole forces, dipole-dipole forces and hydrogen bonding 27. Based on their boiling points , which of the following compounds has the strongest dipole- dipole interactions? A. acetonitrile B. butane C. dimethyl ether D. methyl chloride E. propane Molecule Formula Boiling Point (K) acetonitrile CH 3 CN 355 butane CH 3 CH 2 CH 2 CH 3 135 dimethyl ether CH 3 OCH 3 248 methyl chloride CH 3 Cl 249 propane CH 3 CH 2 CH 3 231

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10 28. Which of these substances will dissolve better in CH 3 (CH 2 ) 4 CH 3 than in water? I. I 2 II. KBr III. A. I only B. II only C. III only D. II and III only E. I and III only 29. Rank the following compounds in order of increasing solubility in water: I II III A. I < II < III B. II < III < II C. II < I < III D. III < I < II E. III < II < I 30. Which of these forces is most responsible for the high solubility of potassium bromide in water? A. London dispersion forces B. ion-dipole forces C. hydrogen bonding D. dipole-dipole forces E. metallic bonding

11 31. When a covalent bond forms between two atoms, the potential energy of the system ________. To break a bond, energy must be _________. A. Decreases, released B. Decreases, added C. Increases, released D. Increases, added E. Stays the same, constant 32. What is the hybridization of the central atom in the phosphorus pentafluoride molecule? A. s B. sp C. sp 3 d D. sp 2 E. sp 3 33. What is the hybridization of the indicated central oxygen atom in the structure below? A. sp B. sp 2 C. sp 3 D. sp 3 d E. sp 3 d 2 34. The angles between sp 2 orbitals are _________ . A. 45° B. 90° C. 109.5° D. 120° E. 180° Continue to the next page. There are 35 questions on the exam.

12 35. Which of the following drawings best depicts sodium chloride dissolved in water? A B C END OF EXAM. You have version A of the exam. Please bubble A for your exam version.

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