1. (6 pts) A sample of gas with a volume of 750 ml exerts a pressure of 756 mm Hg at 30.0 0 C. What pressure (atm) will the sample exert when it is compressed to 250 ml and cooled to -25.0 0 C? a) 1.3 x 10 3 atm b) 2.44 atm c) 8.35 atm d) 4.21 x 10-3 atm e) 86.5 atm 2. (6 pts) Consider a cylinder fitted with a moveable piston that can expand against the atmosphere. The initial pressure, volume and absolute temperature inside the cylinder are P 1, V 1 and T 1. What is the new temperature of the system when the pressure is increased to three times the original pressure and the volume is decreased to one half of the original volume? a) 2.25 T 1 b) 3 T 1 c) 1/5 T 1 d) 1.5 T 1 e) 6 T 1 3. (7 pts) A badly tuned automotive engine can release 50 moles of carbon dioxide per hour. At 35 0 C, what volume of carbon dioxide in a six-hour period (driving from Columbus to Chicago) is released if the atmospheric pressure is 748 mm Hg? a) 2.5 x 10 5 L b) 7.7 x 10 3 L c) 1.3 x 10 3 L d) 10 L e) 5.3 x 10 5 L 1
4. (5 pts) Which of the following statements about ideal gases is true? a) Equal volumes of gases at the same temperature and pressure contain different numbers of molecules. b) The volume of a fixed quantity of gas maintained at constant pressure is inversely proportional to temperature. c) The average kinetic energy of gas molecules is greater than the energy of attraction of gas molecules. d) Standard temperature and pressure are 25.0 o C and 1.0 atm e) In a given sample of an ideal gas, gas molecule behavior is dependent upon molecular attraction and repulsion. 5. (7 pts) The safety air bags in automobiles are inflated by nitrogen gas generated by the rapid decomposition of sodium azide, NaN 3. 2 NaN 3 (s) 2 Na(s) + 3 N 2 (g) If an air bag has a volume of 48 L and is to be filled with nitrogen gas at a pressure of 1.15 atm at a temperature of 27.0 0 C, how many grams of NaN 3 must be decomposed? (MW NaN 3 = 65.00, Na = 23.00, N 2 = 28.00) a) 97 g b) 48 g c) 25 g d) 73 g e) 12 g 6. (6 pts) A 1.00 g sample of SF x has a volume of 270 ml at 745 mm Hg and 75 0 C. What is the value of x? (Atomic weights: S = 32.06, F = 19.00) a) 1 b) 2 c) 3 d) 4 e) 6 2
7. (6 pts) A mixture of 40.0 g helium and 40.0 g argon occupies 3.75 L at 75.0 0 C. What is the partial pressure (atm) of argon? (AW: He = 4.00, Ar = 40.00) a) 7.61 atm b) 9.42 atm c) 27.4 atm d) 81.8 atm e) none of the above 8. (5 pts) Which of the following is not a postulate of the kinetic molecular theory of gases? a) Gases consist of discrete particles that are in constant chaotic motion. b) The molecules possess a volume that is negligibly small compared to the volume of the container. c) The average kinetic energy of the molecules is directly proportional to the absolute temperature. d) The pressure and volume are inversely related. e) All of the above are postulates of the kinetic molecular theory of gases. 9. (6 pts) The van der Waal s constants for three gases are listed below: a ( L 2 atm/mol) b (L/mol) A 12.56 0.08710 B 1.345 0.03219 C 6.714 0.05636 From your knowledge of the physical significance of a and b, intermolecular forces and the sizes of atoms and molecules, identify the gases. The possibilities are SO 2, Ar and CH 3 CH 2 OH. Which of the following statements are correct? a) There is insufficient information to identify the gases. b) A is CH 3 CH 2 OH and B is Ar. c) A is Ar and B is CH 3 CH 2 OH. d) A is SO 2 and B is CH 3 CH 2 OH. e) A is CH 3 CH 2 OH and B is SO 2. 3
10. (7 pts) A gas of unknown molecular mass was allowed to effuse through a small opening under constant pressure conditions. It required 62 s for 1.0 L of the unknown gas to effuse. Under identical conditions, it required 31 s for 1.0 L of oxygen gas to effuse. Calculate the molar mass (g/mol) of the unknown gas. a) 45 g/mol b) 256 g/mol c) 175 g/mol d) 325 g/mol e) 128 g/mol 11. (6 pts) Select the member of each pair with stronger intermolecular forces. CH 4 CCl 4 CH 3 COCH 3 CH 3 CH 2 CH 3 H 2 O H 2 S a) CH 4 CH 3 CH 2 CH 3 H 2 O b) CCl 4 CH 3 COCH 3 H 2 O c) CCl 4 CH 3 COCH 3 H 2 S d) CH 4 CH 3 COCH 3 H 2 S e) CH 4 CH 3 COCH 3 H 2 O 12. (6 pts) Which of the following is true? I. Two of the following molecules can form hydrogen bonds: CH 3 F, CH 3 NH 2, CH 3 OH, CH 3 Br. II. HBr has a higher boiling point than HI. III. Ethyl alcohol (CH 3 CH 2 OH) has a lower boiling point than ethylene glycol (HOCH 2 CH 2 OH). IV. Propyl alcohol (CH 3 CH 2 CH 2 OH) has a higher boiling point that isopropyl alcohol (CH 3 ) 2 CHOH a) I, II, IV b) I, II, III c) II, III, IV d) I, III, IV e) III, IV 13. (5 pts) If a substance has weak molecular forces, it has a boiling point, a heat of vaporization and a vapor pressure. a) low large low b) high large high c) low small high d) high small low e) high large low 4
14. (7 pts) Calculate the heat (kj) evolved when 50.0 g of steam at 120.0 o C are converted to ice at -30.0 o C. Specific heat ice 2.09 J/g o C ΔH fus (ice) 334 J/g Specific heat water 4.18 J/g o C ΔH vap (liquid water) 2260 J/g Specific heat steam 1.84 J/g o C a) -1.92 x 10 5 kj b) -1.55 x 10 2 kj c) -1.32 x 10 2 kj d) -4.87 x 10 2 kj e) none of the above 15. (7 pts) The vapor pressure of water at 37 0 C is 47.1 torr and its enthalpy of vaporization is 44.0 kj/mol. Calculate the vapor pressure of water at 87 0 C. a) 112 torr b) 256 torr c) 713 torr d) 52 torr e) 505 torr 16. (5 pts) Rutile is a mineral composed of titanium and oxygen. In the unit cell, there are titanium atoms at each corner and a titanium atom at the center. Four oxygen atoms are on the opposite faces of the cell, two are entirely within the cell. What is the chemical formula of this mineral? a) TiO 2 b) Ti 2 O c) TiO d) Ti 3 O 2 e) Ti 3 O 4 5
For question 17, sketch the phase diagram: (A) triple point = 20 0 C, 0.03 atm (B) critical point = 150 0 C, 30 atm 30 (C) normal melting point = -20 0 C (D) normal boiling point = 80 0 C (E) Sublimation at -40 0 C requires 1.0 0.008 atm Pressure (atm) 0.03 (not to scale) 0.008 (7 pts) Which of the following statements is correct? -50 0 50 100 150 Temperature ( 0 C) a) The melting point of the solid increases as pressure is increased. b) Line AC represents sublimation. c) As the pressure is increased from 0.0002 atm to 40 atm at 60 0 C, two phase changes occur. d) The solid is denser than the liquid. e) As the temperature is increased from -40 0 C to 125 0 C at 0.9 atm, two phase changes occur. 18. (7 pts) An element crystallizes in a face centered cubic lattice and the edge length of the unit cell is 5.59 x 10-8 cm. The density is 3.19 g/cm 3. What is the element? a) He b) Ne c) Ar d) Kr e) Xe 19. (5 pts) Which of the following statements are false? I. The hexagonal close packed structure is ABABAB, each particle has 12 nearest neighbors and there is 48% open space. II. For a face centered structure, the relationship between edge length (l) and the radius of a particle is l = 4r/ 2. III. Ionic solids conduct electricity. IV. Molecular solids generally have lower melting points than covalent network solids. V. There is one atom per unit cell for a simple cubic unit cell. a) I, III b) III, V c) II, IV d) I, V e) II, V 6
20. (5 pt) Choose the member of each pair that is expected to have the higher normal melting point. NaCl or C CO 2 or SiO 2 O 2 or Na Li or H 2 O a) NaCl CO 2 O 2 H 2 O b) NaCl SiO 2 Na Li c) C CO 2 Na Li d) NaCl SiO 2 O 2 H 2 O e) C SiO 2 Na Li 21. (5 pts) The lattice energy of aluminum trifuloride is 5220 kj/mol. The heat of solution is -27 kj/mol at 25 0 C. Determine the heat of hydration (kj/mol). a) 5247 kj/mol b) 5193 kj/mol c) 0 kj/mol d) -5193 kj/mol e) -5247 kj/mol 22. (6 pts) Which of the following statements about these compounds is false? a) A solution containing 35 g of B in 85 g H 2 O at 80 o C is unsaturated. b) The heat of solution of B is endothermic. c) If a saturated solution of A is heated from 10 o C to 90 o C, the solution remains saturated. d) 20 g of C can be completely dissolved in 100 g of H 2 O at 20 o C. e) None of the above statements are false. 7
23. (5 pts) Which of the following of each pair is expected to be more soluble in water? CH 3 OH or CH 3 Br SiO 2 or H 2 CO 3 C 6 H 12 or C 6 H 12 O 6 a) CH 3 OH SiO 2 C 6 H 12 O 6 b) CH 3 OH H 2 CO 3 C 6 H 12 O 6 c) CH 3 Br SiO 2 C 6 H 12 d) CH 3 Br SiO 2 C 6 H 12 O 6 e) CH 3 OH H 2 CO 3 C 6 H 12 24. (6 pts) What is the molality of a 1.06 M aqueous solution of sugar (C 6 H 12 O 6, 342.3 g/mol) which has a density of 1.14 g/ml? a) 1.36 molal b) 1.06 molal c) 0.927 molal d) 0.634 molal e) 0.442 molal 25. (7 pts) Calculate the mole fraction of ethanol in the vapor phase at 63.5 0 C for an ideal solution containing 96.0 gm of pure methanol (CH 3 OH, 32.0 g/mol) and 92.2 gm of pure ethanol (CH 3 CH 2 OH, 46.1 g/mol). The vapor pressure of methanol and ethanol at 63.5 0 C is 717.2 mm and 400.0 mm mercury, respectively. a) 0.943 b) 0.701 c) 0.466 d) 0.271 e) none of the above 8
26. (5 pts) What is the boiling point change for a solution containing 0.328 moles of naphthalene (a nonvolatile, nonionizing compound) in 250. g of liquid benzene (K b = 2.53 0 C/m, BP = 80.1 0 C) a) 3.32 0 C b) 7.41 0 C c) 1.93 0 C d) 4.31 0 C e) 10.7 0 C 27. (6 pts) When a 20.0 g sample of an unknown compound is dissolved in 500.0 g of benzene, the freezing point of the resulting solution is 3.77 0 C. The freezing point of pure benzene is 5.48 0 C and the K f for benzene is 5.12 0 C/m. Calculate the molar mass of the unknown compound. a) 160. g/mol b) 80.0 g/mol c) 100. g/mol d) 140 g/mol e) 120 g/mol 28. (5 pts) The molar mass of a solid as determined by freezing point depression is 10% higher than the true molar mass. Which of the following experimental errors could not account for this discrepancy? a) Not all the solid was dissolved. b) More than the recorded amount of solvent was pipetted into the solution. c) The solid dissociated slightly into two particles when it dissolved. d) Some solid was left of the weighing paper. e) Before the solution was prepared, the container was rinsed with solvent and not dried. 9
29. (7 pts) Cox-1 is a protein that acts as an enzyme to speed up the production of prostaglandins. A solution contains 2.88 g of Cox-1 in 125 ml of water. This solution has an osmotic pressure of 24.8 mm Hg at 27 0 C. What is the molecular weight of this sample of Cox-1? a) 4.81 X 10 3 g/mol b) 3.20 x 10 4 g/mol c) 8.05 x 10 5 g/mol d) 5.75 x 10 3 g/mol e) 1.74 x 10 4 g/mol 30. (6 pts) Which of the following solutions should have the highest freezing point? a) 0.01 m KBr b) 0.005 m (NH 4 ) 3 PO 4 c) 0.008 m MgCl 2 d) 0.01 m glucose e) 0.006 Ca(OH) 2 10
Helpful Information R = 0.08206 L-atm/mol-K = 8.3145 J/mol-K Avogadro s number = 6.02 x 10 23 particles/mol 1 Angstrom = 1 x 10-10 m = 1 x 10-8 cm T(K) = T( 0 C) = 273.15 K Molar volume at STP = 22.4 L density of Hg = 13.55 g/cm 3 at 20 0 C PV = nrt P i = Χ i P total [ P + n 2 a/v 2 ] [ V nb ] = nrt KE = ½ mv 2 KE avg = ½ mµ 2 µ = ( 3RT/MW ) 1/2 ln(p 2 /P 1 ) = ΔH vap /R(1/T 1-1/T 2 ) 11