CHEM 101 WINTER 09-10 MAKEUP EXAM On the answer sheet (Scantron) write you name, student ID number, and recitation section number. Choose the best (most correct) answer for each question and enter it on your answer sheet. Avogadro s Number: 6.022 10 23 mol -1 R = 0.0821 L atm mol -1 K -1 1 atm = 760 Torr = 760 mm Hg P 1 V 1 / n 1 T 1 = P 2 V 2 / n 2 T 2 PV = nrt d = PM / RT 1. Please chose the letter a as your answer for this question. 2. VSEPR Theory predicts that the shape of a molecule, determined by both the electron pair geometry and the molecular geometry, is the result of a. the minimization of the repulsion of electrons in the valence shell of the central atom. b. the momentum of the electrons in the valence shell of the central atom. c. the London force attraction of electrons in the valence shell of the central atom to those in the terminal atoms. d. the mutual attraction of the electrons in the valence shell of the central atom. e. the distance of the lone pairs in the terminal atoms from the electrons in the valence shell of the central atom. 3. According to VSEPR Theory, predict the electron pair geometry for two, four, and six electron domains, respectively, in molecules not having lone pairs of electrons on the central atom. a. they are all tetrahedral b. angular, tetrahedral, trigonal bipyramidal c. linear, tetrahedral, octahedral d. linear, tetrahedral, hexagonal e. linear, tetrahedral, trigonal bipyramidal 4. Which of the following central atoms would not accommodate more than eight electrons in any of its compounds? a. nitrogen b. selenium c. sulfur d. phosphorus e. arsenic 5. Use VSEPR Theory to predict the X-A-X angles for the following compounds: H 2 S SiBr 4 HCN a. 104.5, 109.5, 180 b. 180, 109.5, 120 c. 109.5, 90, 109.5 d. 109.5, 109.5, 109.5 e. 180, 90, 120
6. In VSEPR Theory, the electron-pair geometry of a molecule will never be the same as its molecular geometry when there is a. no lone pair of electrons on the terminal atoms. b. at least one lone pair of electrons on the central atom. c. a central atom which is a nonmetal. d. a lone pair of electrons on one of the terminal atoms e. no lone pair of electrons on the central atom. 7. For which of the following will the electron-pair geometry be identical to the molecular geometry? a. SF 4 b. CFClBrI c. H 2 S d. BH 2 e. H 2 O 8. In a molecule with trigonal bipyramidal electron-pair geometry, lone pairs on the central atom are preferentially placed in the equatorial position rather than the axial position because a. of the fact that there are no lone pair electrons on the terminal atoms b. terminal atoms cannot have lone pairs c. of the net sum of all the electron pair interactions in the valence shell of the central atom d. of the magnetic polarity quantum number of the terminal atoms e. there can be no lone pairs on the central atom to obtain a trigonal bipyramidal electronpair geometry 9. Which of the following correctly list the relative strengths of electron-pair repulsions in order of increasing magnitude? a. lone pair-lone pair < bonding pair-bonding pair < lone pair-bonding pair b. bonding pair-bonding pair < lone pair-bonding pair < lone pair-lone pair c. lone pair-lone pair < lone pair-bonding pair < bonding pair-bonding pair d. lone pair-bonding pair < lone pair-lone pair < bonding pair-bonding pair e. bonding pair-bonding pair < lone pair-lone pair < lone pair-bonding pair 10. In which of the following are both of the molecules non-polar? a. HI HF b. N 2 NCl 3 c. H 2 Se CF 4 d. BH 3 BeH 2 e. GeF 4 PH 3 11. London (dispersion) forces may occur a. only between molecules in which hydrogen bonding is also possible. b. only between molecules with nonpolar bonds. c. between any combination of covalent molecules. d. only between molecules with polar bonds. e. only between molecules with multiple covalent bonds.
12. Which of the following sets of molecules contains at least one compound that will not exhibit extensive hydrogen bonding? a. H 3 C-OH, H 2 O, NH 3 b. H 2 O, HF, H 2 N-CH 3 c. H 2 O, HF, HCl d. H 2 O, HF, H 2 N-CH 2 -NH 2 e. H 2 O, HF, NH 3 13. What is the one type of intermolecular force that must be overcome to allow the vaporization of liquid bromine as well as the vaporization of water? a. hydrogen bonding b. ion-dipole forces c. dipole-dipole attractions d. London (dispersion) forces e. covalent bonds 14. Based on temperature, there are four main layers to our atmosphere. Which of the following is the correct name for the layer in which we live? a. isopiestosphere b. troposphere c. barosphere d. thermopause e. tropopause 15. One atmosphere of pressure is equal to 760 mm Hg. This unit is used in the common barometer and manometer. Determine the height (in mm) of a column of carbon tetrachloride in a barometer if the pressure is 1.11 atmospheres. The densities of mercury and carbon tetrachloride are 13.55 g/cm 3 and 1.58 g/cm 3, respectively. a. 1342 b. 1.1 10 4 c. 2.0 10 4 d. 988 e. 7235 16. If, at constant temperature, the volume of a flask equipped with a moveable piston is decreased to 1/9 its original volume, what must happen to the pressure of the gas inside? a. It is increased by a factor of 3. b. It is increased by a factor of 9. c. It remains the same as the original pressure. d. It is reduced to 1/3 of the original pressure. e. It is reduced to 1/9 of the original pressure. 17. Which statement about ideal gases and the gas laws is false? a. Most gases are ideal, or almost ideal gases at room temperature and atmospheric pressure. b. Variables that appear in the laws are temperature, pressure, volume, and amount of gas. c. The laws are summarized as equations that describe the behavior of ideal gases. d. The smallest deviation from ideal gas behavior occurs at low temperature and high pressure. e. The laws describe the macroscopic behavior of ideal gases.
18. If a 3.5-liter sample of gas experiences an increase in pressure from 0.555 atm to 1.74 atm at 25 C, what is the resulting volume at 298 K? a. 1.12 L b. 3.20 L c. 0.48 L d. 9.36 L e. 20.0 L 19. With reference to the kinetic-molecular theory of gases, which of the following statements is false? a. Gas molecules move randomly in all possible directions at various speeds. b. Under ideal gas conditions, the distance between gas molecules is smaller than the diameter of the gas molecules. c. The average kinetic energy of gas molecules increases as the temperature increases. d. The forces of attraction and repulsion between separate gas molecules are minimal. e. No energy is lost when gas molecules collide with each other. 20. What is the pressure (in atm) exerted by a 5.00 mole sample of gas that occupies 50.0 L at 273 K? a. 2.24 b. 80.7 c. 38.1 d. 9.60 e. 40.3 21. Suppose that at STP a gas occupies 7.50 L. At what temperature ( K) will the same gas occupy 15000 ml at 760 Torr? a. 546 b. 273 c. 819 d. 6.22 10 5 e. 1118 22. Determine the density of krypton gas (Kr) at STP? a. 1.43 g/l b. 3.74 g/l c. 1.31 g/l d. 716 g/l e. 1090 g/l 23. If a 25.0 gram sample of zinc is reacted with excess HCl, what volume of hydrogen gas would be evolved at 0.9 atm and 313 K? Zn (s) + 2 HCl (aq) ZnCl 2 (aq) + H 2 (g) a. 2.85 L b. 10.9 L c. 8.56 L d. 6.85 L e. 0.075 L
24. What is a possible molecular formula for a gas that has a density of 1.82 g/l at 21.0 C and 1.00 atm? a. Cl 2 b. CO 2 c. O 2 d. CH 4 e. CO 25. For a gas mixture containing 1.0 M concentration of each of the following, He, Ne,,Ar, and Kr, at room temperature a. the lightest gas will have the lowest partial pressure. b. the total pressure is equal to 4 times the partial pressure of krypton. c. the total pressure is equal to 4 times the sum of the partial pressures. d. the lightest gas will have the highest partial pressure. e. the partial pressures of the gases at equilibrium are different from one another. 26. A mixture of N 2 (g) and Ar (g) exerts a total pressure of 0.300 atm. If the mole fraction of argon is 0.625, what is the partial pressure (in atm) of N 2? a. 7.14 b. 1.63 c. 0.113 d. 0.875 e. 0.606
CHEM 101 WINTER 09-10 MAKEUP EXAM VERSION 03-03-10 Answer Section SHORT ANSWER 1. ANS: a PTS: 1 MULTIPLE CHOICE 2. ANS: A PTS: 1 TOP: 9.2 Predicting Molecular Shapes: VSEPR 3. ANS: C PTS: 1 TOP: 9.2 Predicting Molecular Shapes: VSEPR 4. ANS: A PTS: 1 TOP: 9.2 Predicting Molecular Shapes: VSEPR 5. ANS: A PTS: 1 TOP: 9.2 Predicting Molecular Shapes: VSEPR 6. ANS: B PTS: 1 TOP: 9.2 Predicting Molecular Shapes: VSEPR 7. ANS: B PTS: 1 TOP: 9.2 Predicting Molecular Shapes: VSEPR 8. ANS: C PTS: 1 TOP: 9.2 Predicting Molecular Shapes: VSEPR 9. ANS: B PTS: 1 TOP: 9.2 Predicting Molecular Shapes: VSEPR 10. ANS: D PTS: 1 TOP: 9.5 Molecular Polarity 11. ANS: C PTS: 1 TOP: 9.6 Noncovalent Interactions and Forces Between Molecules 12. ANS: C PTS: 1 TOP: 9.6 Noncovalent Interactions and Forces Between Molecules 13. ANS: D PTS: 1 TOP: 9.6 Noncovalent Interactions and Forces Between Molecules 14. ANS: B PTS: 1 TOP: 10.1 The Atmosphere 15. ANS: E PTS: 1 TOP: 10.2 Properties of Gases 16. ANS: B PTS: 1 TOP: 10.4 The Behavior of Ideal Gases 17. ANS: D PTS: 1 TOP: 10.4 The Behavior of Ideal Gases 18. ANS: A PTS: 1 TOP: 10.5 The Ideal Gas Law 19. ANS: B PTS: 1 TOP: 10.5 The Ideal Gas Law 20. ANS: A PTS: 1 TOP: 10.5 The Ideal Gas Law 21. ANS: A PTS: 1 TOP: 10.5 The Ideal Gas Law 22. ANS: B PTS: 1 TOP: 10.5 The Ideal Gas Law 23. ANS: B PTS: 1 TOP: 10.6 Quantities of Gases in Chemical Reactions 24. ANS: B PTS: 1 TOP: 10.7 Gas Density and Molar Masses 25. ANS: B PTS: 1 TOP: 10.8 Gas Mixtures and Partial Pressures 26. ANS: C PTS: 1 TOP: 10.8 Gas Mixtures and Partial Pressures