Unformatted text preview: CHM-102 NAME • • • • • • KEY Exam I Form A Summer 2010 Raw Score T-Score You will have 70 minutes to complete the exam. There is one best answer to each question and all questions are worth the same number of points. Sign your name on the answer sheet above the General Purpose logo on the front. Print and fill in your name (last name-space-first name) on the back of your answer sheet. Be sure to mark the correct answers on your exam booklet so you can compare your answers to the answer key. An answer key will be posted immediately following the test at the course website as well as outside DO-236. 1. If the central atom in a molecule has sp2 hybridization, how many electron domains must the central atom have? a. one b. two c. three d. none of these Use the following Lewis dot structures to answer questions 2 & 3 F F B
F S F
Cl Cl C Cl Cl II III IV 2. Which of the above molecules have the same hybridization on the central atom? a. I, II, and III only c. I and III only b. II, III and IV only d. none of them 3. Which of the above molecules are NON-POLAR? a. b. c. d. I and IV only I, II and IV only IV only All of them are non-polar 4. Which of the following molecules has tetrahedral molecular geometry? a. CCl4 b. XeF4 c.
5. PH3 d. only a & b
Electrons in __________ bonds remain localized between two atoms. Electrons in __________ bonds can become delocalized between more than two atoms. A) pi, sigma B) sigma, pi C) pi, pi D) sigma, sigma 6. Determine the number of σ and π bond(s) in the molecule below. : O:
H C C C H a. 5 σ, 5π b. 7 σ, 3π : N H c. 10 σ, 3π d. 7 σ, 2π 7. For the molecule shown in question 6, which of the following statements is correct? a. b. c. d. All of the carbon atoms have the same molecular geometry. All of the carbon atoms have sp2 orbital hybridization The molecular geometry around N is trigonal pyramidal The lone pair electrons on O are delocalized 8. When the volume of a gas is increased at constant temperature, the pressure a. b. c. d. decreases, because the gas molecules get smaller. decreases, because fewer gas molecules collide with the container walls every second. increases, because the average kinetic energy of the molecules increases. increases, because the intermolecular forces become stronger. 9. What volume does a sample of He gas (9.40 grams) occupy at 150 °C and 760 torr. a. 0.038 L b. 326 L c. 1.41 L d. 81.6 L 10. If 1.40 grams of He was added to the container in question 9, but the pressure and volume remained constant, what would happen to the temperature? a. the temperature would not change c. the temperature would go down b. the temperature would go up d. can’t tell from the info provided 11. A sample of O2 gas is originally at 25 °C and 1.00 atm pressure in a 2.5 L container. It is allowed to expand until the pressure is 0.85 atm and the temperature is 15 °C. What is the new volume of O2? A) 3.0 L B) 2.8 L C) 2.6 L D) 2.1 12. The density of ammonia gas (MW=17) in a 4.32 L container at 837 torr and 45.0 °C is: A) 3.86 g/L B) 0.717 g/L C) 0.432 g/L D) 0.194 g/L 13. A SCUBA tank contains compressed air at a total pressure of 100 atm and is at the same temperature (25 °C) as this classroom. Which of the statements correctly completes the following sentence? The partial pressures of N2 and O2 of the air in the SCUBA tank a. are the same as the partial pressures of N2 and O2 of the air in this classroom. b. are less than the partial pressures of N2 and O2 of the air in this classroom. c. are greater than the partial pressures of N2 and O2 of the air in this classroom. d. cannot be calculated without knowing the volume of the SCUBA tank. 14. What volume of NOBr gas at 0 oC and 1.00 atm would be generated by reacting 0.500 moles of Br2(g) according to the following reaction equation? 2 NO(g) + Br2(g) a. 11.2 L b. 22.4 L 2 NOBr(g) c. 33.6 L d. 44.8 L 15. A vessel contained N 2 , Ar, He, and Ne. The total pressure in the vessel was 987 torr. The partial pressures of nitrogen, argon, and helium were 44.0, 486, and 218 torr, respectively. The partial pressure of neon in the vessel was: A) 42.4 torr B) 521 torr C) 19.4 torr D) 239 torr 16. The distribution of molecular speeds for three unknown gases X, Y, and Z was determined at the same temperature. From the Botlzman Distributions shown on the graph below, determine which of the following statements are correct according to kinetic molecular theory.
X Y Z i. ii. iii. iv. v. The order of molar mass is X > Y > Z The order of molar mass is Z > Y > X The average kinetic energy of gas X is greater than gas Y and Z. The average kinetic energy of gas Z is greater than gas X and Y. The average kinetic energy for all three gases is the same. b. ii and iv only c. i and iii only d. none are correct a. i and v only 17. Nitrogen gas (N2) effuses through a pinhole at the rate of 12 mol/hr. What is the effusion rate for ethylene gas (C2H4) under identical conditions? a. 12 mol/hr b. 24 mol/hr c. 36 mol/hr d. 48 mol/hr 18. The van der Waals equation for real gases recognizes that __________. A) gas particles have non-zero volumes and interact with each other B) molar volumes of gases of different types are different C) the molecular attractions between particles of gas decreases the pressure exerted by the gas D) all of the above statements are true 19. Which of the following substances has the highest boiling point? a. H2O b. CO2 c. H2S d. NH3 20. Which of the molecules pictured below could not exhibit hydrogen bonding as one of its intermolecular forces? a. i, ii, iii, iv b. i and ii only c. iii and iv only d. iv only 21. Which of the following statements about liquids is not correct? a. The viscosity of a liquid will decrease with increasing temperature. b. Liquids with large intermolecular forces will have high surface tension. c. The intermolecular forces in liquids are strong enough to hold molecules relatively close together, but not strong enough to keep molecules from moving past each other. d. Liquids composed of shorter chain molecules will generally have higher viscosity than liquids with longer chain molecules. Important Formulas and Constants
P1V1 P2V2 = n1T1 n 2 T2 PV = nRT PV = mRT M
Xa = na nT M= dRT P PT = P1 + P2 + P3 + ...
2 ⎡ ⎛n⎞ ⎤ ⎢ P + a⎜ ⎟ ⎥[V − bn] = nRT ⎝V ⎠ ⎥ ⎢ ⎣ ⎦ Pa = X a PT r1 = r2 M2 M1 1 in = 2.54 cm 1 qt = 0.946 L 453.6 g = 1 lb R = 0.0821 L·atm·K-1·mol-1 NA = 6.02 x 1023
K = ºC + 273 1 atm = 760 mm Hg = 760 torr = 101.3 kPa ...
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- Summer '09
- Chemistry, Molecule, Kinetic theory, average kinetic energy