State University of New York at Binghamton, Department of Chemistry Chemistry 108, Introductory Chemistry II, Exam 1, February 26, 2015 Version A

State University of New York at Binghamton, Department of Chemistry Chemistry 108, Introductory Chemistry II, Exam 1, February 26, 2015 Version A Write Version A on top of your Scantron. The Exam will be graded based on the version written on the Scantron. Only non-graphing calculators are allowed on this Exam. You have 90 minutes to complete this exam. DO NOT SEPARATE THE EXAM. Answer ALL questions. Fill in the appropriate selection on your Scantron form. 1. Which of the following will have the largest cation-anion attraction? a. NaF b. NaCl c. NaBr d. NaI e. CsCl 2. A solution is prepared by adding 1.50 mol glucose, which is not volatile, to 3.50 mol water. What is the vapor pressure of this solution at 25 °C given that the vapor pressure of pure water is 23.8 torr? a. 7.00 torr b. 16.7 torr c. 10.2 torr d. 7.14 torr e. 34.0 torr 3. Which statement does not describe a simple cubic unit cell? a. It results from square packing of atoms in layers b. The atoms lie at the corners of a cube c. Each atom has 6 nearest neighbors d. The stacking pattern can be represented by aaaaa e. Each unit cell contains 8 atoms 4. Arrange the three ionic compounds sodium chloride, potassium chloride, and rubidium chloride in order of increasing melting point. a. NaCl RbCl KCl b. KCl RbCl NaCl c. NaCl KCl RbCl d. RbCl KCl NaCl e. RbCl NaCl KCl 5. Coulomb’s law states that the interaction energy between ions depends ____________ a. Only on the ionic charges b. Only on the distance between the ions c. Directly on both the ionic charges and the distance between the ions d. Directly on the distance between the ions and inversely on the ionic charges e. Directly on the ionic charges and inversely on the distance between the ions 6. Which of the following unit cells has the highest packing efficiency? a. Simple cubic b. Face-centered cubic c. Body-centered cubic d. Both face-centered and body-centered cubic e. Simple, face-centered, and body centered cubic all have the same packing efficiency 7. One reaction that occurs in an automobile catalytic converter is the conversion of carbon monoxide to carbon dioxide. How could the rate of this reaction be expressed correctly in terms of the rate at which the concentration of a reactant or product changes? 2CO(g) + O2(g) → 2CO2(g) a. Rate = Δ[CO]/Δt b. Rate = -Δ[CO]/Δt c. Rate = Δ[O2]/Δt d. Rate = -½Δ[CO]/Δt e. Rate = 2Δ[CO2]/Δt 8. A hydration sphere forms around an ion in aqueous solution due to ________________ a. Ion-ion interactions b. Dispersion forces c. Dipole-dipole interactions d. Ion-dipole interactions e. Ion-induced dipole interactions 9. An ideal solution is prepared by mixing 75 g of methanol (CH3OH) with 25 g of ethanol (CH3CH2OH). Both chemicals are volatile. Use the following data to determine the vapor pressure of this solution at 20 °C. Substance Vapor Pressure at 20 °C (torr) Methanol 92 Ethanol 45 a. 69 torr b. 57 torr c. 80 torr d. 73 torr e. 83 torr 10. A scientist conducts an experiment to determine the rate of NO formation in the reaction: N2(g) + O2(g) →2NO(g) If the initial concentration of N2 was 0.500 M and the concentration of N2 was 0.450 M after 0.100 s, what is the average rate of NO formation? a. 0.500 M/s b. 1.00 M/s c. 5.00 M/s d. 10.0 M/s e. 0.250 M/s 11. If a sample of water was at 1 atm and 50 °C, which of the following would cause the water to freeze? a. Increasing the pressure to 218 atm, and then decreasing the temperature to 0 °C b. Decreasing the pressure to 0.0010 atm, and then decreasing the temperature to 0 °C c. Decreasing the pressure to 0.070 atm, and then increasing the temperature to 100 °C d. Decreasing the pressure to 0.050 atm, and then decreasing the temperature to 0 °C e. Decrease the pressure to 0.0060 atm, and keep the temperature the same 12. The aroma from almonds and cherries is due in part to a compound called benzaldehyde. A graph of the natural logarithm of the vapor pressure of benzaldehyde vs 1/temperature produces a straight line with a slope of -5870.99 K. What is the enthalpy of vaporization of benzaldehyde? a. +47.3 kJ/mol b. +481 kJ/mol c. +48811 kJ/mol d. +43.7 kJ/mol e. +48.8 kJ/mol 13. Which of the following aqueous solutions will have the lowest freezing point? a. 0.1 m magnesium sulfate, MgSO4 b. 0.1 m potassium chloride, KCl c. 0.08 m magnesium chloride, MgCl2 d. 0.04 m sodium sulfate, Na2SO4 e. 0.05 m sodium chloride, NaCl 14. For the rate law Rate = k[A][B]3 , the partial order with respect to A is ___________, the partial order with respect to B is ___________, and the total order is ____________. a. 0, 3, 3 b. 1, 1/3, 4/3 c. 1, 1, 2 d. 3, 1, 3 e. 1, 3, 4 15. Sublimation occurs in going from region _______ to ________ a. I to II b. I to III c. II to III d. III to II e. III to I 16. A solution is made by dissolving 100 g of essentially nonvolatile ethylene glycol (C2H6O2) in 500 g of water. What is the resulting freezing point of the solution (Kf = 1.86 °C/m) a. -5.99 °C b. -1.86 °C c. -0.372 °C d. -1.61 °C e. -3.23 °C 17. In the unit cell of silver iodide, ________________ a. All of the octahedral holes are filled with cations b. Half of the octahedral holes are filled with cations c. Half of the tetrahedral holes are filled with cations d. All of the tetrahedral holes are filled with cations e. Cations occupy standard atomic positions in the unit cell, not holes 18. Which of the following compounds is capable of hydrogen bonding? a. CH3OCH3 b. CH3COCH3 c. H2CO d. CH3CH2OH e. CH3F 19. A newspaper article suggested using fertilizer such as ammonium sulfate or ammonium nitrate to lower the melting point of ice on sidewalks because many of the deicing salts can damage lawns and sidewalks. Which of the following compounds would give the largest freezing point depression when 100 g of the compound are dissolved in 1 kg of solvent? a. NH4NO3 (80.1 g/mol) b. (NH4)2SO4 (132.1 g/mol) c. MgSO4 (120.4 g/mol) d. MgCl2 (95.2 g/mol) e. CaCl2 (111.0 g/mol) 20. Which of these could be the units of the rate constant for a first-order reaction? a. M/s b. 1/Ms c. 1/Ms2 d. Ms e. 1/s 21. Viscosity is a measure of a substance’s _______________ a. Ability to resist changes in its surface area b. Surface tension c. Resistance to flow d. Compressibility e. Color 22. Use the following data to calculate the lattice energy of MgCl2, for the reaction of Mg(s) + Cl2(g) → MgCl2(s) (ΔHf = -643 kJ/mol). Reaction Enthalpy Mg(s) → Mg(g) +148 kJ/mol Cl2(g) → 2Cl(g) +244 kJ/mol Mg(g) → Mg+ (g) + e- +738 kJ/mol Mg+ (g) → Mg2+(g) + e- +1451 kJ/mol Cl(g) + e- → Cl- (g) -349 kJ/mol Mg+ (g) + 2Cl- (g) → MgCl2(s) ???? a. -1240 kJ/mol b. -2526 kJ/mol c. -2875 kJ/mol d. -1075 kJ/mol e. -1589 kJ/mol For questions 23 and 24, use the following picture: 23. In this unit cell, there are ____________ atoms, and the coordination number is __________. a. 1, 6 b. 2, 8 c. 4, 8 d. 3, 12 e. 4, 12 24. If this is a unit cell of aluminum, Al, with an edge length of 404 pm, what is the atomic radius of aluminum? a. 143 pm b. 202 pm c. 286 pm d. 175 pm e. 808 pm 25. Which alcohol should be most soluble in a nonpolar solvent such as hexane, C6H14? a. CH3OH b. CH3CH2OH c. CH3CH2CH2OH d. CH3CH2CH2CH2OH e. CH3CH2CH2CH2CH2OH 26. The freezing point of a 0.0925 m solution of ammonium chloride was found to be -0.325 °C. What is the actual van ‘t Hoff factor for this salt at this concentration? a. 1.89 b. 1.95 c. 2.00 d. 1.80 e. 1.97 27. Which of the following plots indicates that the reaction is second order? a. A b. B c. C d. D e. A and D 28. What pressure of carbon dioxide is required to maintain the carbon dioxide concentration in a bottle of club soda at 0.12 M at 25 °C? (Henry’s Law constant kH = 3.4 x 10-2 M/atm) a. 7.0 atm b. 28.3 atm c. 3.5 atm d. 12.0 atm e. 1.8 atm 29. What is the molarity of a sucrose (C12H22O11) solution that produces an osmotic pressure of 2.65 atm at 25 °C? a. 0.0349 M b. 0.127 M c. 0.0127 M d. 0.108 M e. 0.398 M 30. Band theory of bonding in solids _______________ a. Is an extension of molecular orbital theory b. Describes bonds as rubber bands c. Does not apply to any type of solid other than metals d. Explains bond formation in metals, but not their physical properties e. All of the above are correct 31. Which of the following statements does not correctly identify a factor that affects the boiling point of a pure substance? I. Vapor pressure of the liquid II. Strength of the intermolecular forces III. Enthalpy of vaporization IV. Surface area of the liquid a. I only b. II only c. III only d. IV only e. III and IV 32. Given the following data, determine the rate law for the reaction H2(g) + 2ICl(g) → I2(g) + 2HCl(g) Experiment [H2] (M) [ICl] (M) Rate (M/s) 1 250 325 1.34 2 250 81.25 0.335 3 50 325 0.268 a. Rate = k[H2][ICl] b. Rate = k[H2] 2 [ICl] c. Rate = k[H2][ICl] 4 d. Rate = k[H2] 5 [ICl] e. Rate = k[H2] 5 [ICl] 4 33. Which of the following is a colligative property? I. Osmotic pressure II. Vapor pressure lowering III. Freezing point depression IV. Boiling point elevation a. II, III and IV only b. III and IV only c. II and III only d. I and II only e. I, II, III, and IV 34. Which element would be used to dope germanium (Ge) to produce an n-type semiconductor? a. Ga b. Sn c. Si d. As e. Cu 35. The rate of popcorn popping at different temperatures was found to be described by the Arrhenius equation. How many times faster does the popcorn pop at 210°C compared with that at 180°C when the activation energy is 167 kJ/mol? a. 8.80 x 106 b. 8.38 x 106 c. 1.20 d. 15.7 e. 42.6 36. Which of the following is capable of dipole-dipole interactions? a. CH4 b. CO2 c. H2CO d. SF6 e. NH4 + 37. If an X-ray with a wavelength of 154 pm is diffracted at an angle of 19.3° (not radians), according to the Bragg equation (nλ = 2dsinθ), what is the distance between layers of the crystal that give rise to this diffraction? Assume n = 1 in this problem. a. 233 pm b. 392 pm c. 106 pm d. 154 pm e. 288 pm 38. Dr. Mushibe likes boiled eggs for breakfast, but they take too long to cook, and he is sometimes late to his early morning class. Dr. Mushibe knows that adding table salt, NaCl (58.4 g/mol, 2.16 g/cm3 ), to water (Kb = 0.52 °C/m) increases the temperature at which it boils. Dr. Mushibe figures that you can cook eggs faster at a higher temperature in boiling salty water. What boiling point elevation do you expect if you add 4 tablespoons (1 tablespoon = 14.8 cm3 ) of salt to 16 oz of water (474 cm3 )? a. 14 °C b. 4.8 °C c. 28 °C d. 3.0 °C e. 8.4 °C 39. The alpha form of polonium (Po) has a density of 9.196 g/cm3 and crystallizes in a simple cubic structure. What is the atomic radius of polonium? a. 119 pm b. 266 pm c. 168 pm d. 335 pm e. 419 pm 40. The energy profiles for four different reactions are shown below. The scales are the same for each. Which reaction requires the most energetic collisions to reach the transition state? a. a b. b c. c d. d e. More information is needed to answer Bonus: 41. The half-life for the radioactive decay of U-238 is 4.5 billion years and is first order and is independent of initial concentration. How long will it take for 10% of the U-238 atoms in a sample of U-238 to decay in seconds? a. 6.8 x 108 seconds b. 4.5 x 108 seconds c. 5.9 x 1012 seconds d. 3.6 x 1014 seconds e. 2.1 x 1016 seconds