Chem. 112 spring 2012 Exam 1 7:0am/Odago Wednesday March 7, 2012 Attempt all the questions and fill in your answers correctly on the scantron provided 1. A particular gas exerts a pressure of 4.6 atm. What is this pressure in units of mmhg? a) 5.74 10 mmhg b) 4.42 mmhg c).1 10 mmhg d) 4.0 mmhg e).6 10 mmhg 2. Absolute zero is the temperature at which a) gaseous helium liquefies. b) a straight line graph of P versus 1/V intersects the 1/V axis. c) a straight line graph of V versus 1/P intersects the 1/P axis. d) a graph of P versus V at constant T intersects the V axis. e) a straight line graph of V versus T intersects the T axis.. A gas occupying a volume of 1.50 L exerts a pressure of 700 mmhg at 200 C. Which mathematical expression gives the correct pressure at 6.00 L and 00 C? a) 6.00 L 57 K 700 mmhg 1.50 L 47 K b) c) d) 1.50 L 57 K 700 mmhg 6.00 L 47 K 6.00 L 47 K 700 mmhg 1.50 L 57 K 1.50 L 47 K 700 mmhg 6.00 L 57 K o 6.00 L 00 C o e) 700 mmhg 1.50 L 200 C 4. A gas occupies. L at 2.2 atm. What is the volume at 2.50 atm at constant Temp.? A) 1.67 L B).7 L C) 2.97 L D) 0.268 L E) 18.6 L 5. To what temperature must a balloon, initially at 25 C and 2.00 L, be heated in order to have a volume of 6.00 L at constant pressure? A) 99 K B) 40 K C) 75 K D) 655 K E) 894 K 1
6. What pressure (in atm) will 0.44 moles of CO2 exert in a 2.6 L container at 25 C? A) 0.5 atm B) 4.1 atm C) 4.7 atm D) 8.6 atm E).6 atm 7. Determine the density of NH gas at 45 K and 1.00 atm. A) 2.10 g/l B) 0.477 g/l C) 0.21 g/l D) 2.24 g/l E) 0.851 g/l 8. A mixture of 0.220 moles CO, 0.50 moles H2 and 0.640 moles He has a total pressure of 2.95 atm. What is the partial pressure of H2? A) 1.17 atm B) 0.85 atm C) 1.0 atm D) 0.969 atm E) 0.649 atm 9. A gas mixture contains CO, Ar and H2. What is the total pressure of the mixture, if the mole fraction of H2 is 0.5 and the pressure of H2 is 0.58 atm? A) 1.7 atm B) 0.20 atm C) 0.49 atm D) 0.60 atm E) 2.1 atm 10. Which statement is TRUE about kinetic molecular theory? A) A single particle does not move in a straight line. B) The size of the particle is large compared to the volume. C) The collisions of particles with one another is completely elastic. D) The average kinetic energy of a particle is not proportional to the temperature. 11. The density of nitric oxide (NO) gas at 1.21 atm and 54.1 C is g/l. A) 0.0451 B) 0.740 C) 1.5 D) 0.27 E) 8.2 2
12. A 1.44 g sample of an unknown pure gas occupies a volume of 0.5 L at a pressure of 1.00 atm and a temperature of 100.0 C. The unknown gas is. A) argon B) helium C) krypton D) neon E) xenon 1. What is the average speed (actually the root mean square speed) of a neon atom at 27 C? A) 5.78 m/s B) 19. m/s C) 18 m/s D) 609 m/s 14. What is the temperature of NO 2 gas if the average speed (actually the root meansquare speed) of the molecules is 750 m/s? A) 1.8 K B) 1.04 10 K C) 1.8 10 K D) 1.04 106 K 15. Determine the molality of a solution prepared by dissolving 0.500 moles of CaF2 in 11.5 moles H2O. A) 1.88 m B) 4.5 m C) 5.1 m D) 4.14 m E) 2.41 m 16. Determine the freezing point depression of a solution that contains 0.7 g glycerin (CH8O, molar mass = 92.09 g/mol) in 76 ml of water. Some possibly useful constants for water are Kf = 1.86 C/m and Kb = 0.512 C/m. A) 0.887 C B) 1.65 C C). C D). C E) 0.654 C
17. Give the reason that antifreeze is added to a car radiator. A) The freezing point is lowered and the boiling point is elevated. B) The freezing point is elevated and the boiling point is lowered. C) The freezing point and the boiling point are elevated. D) The freezing point and the boiling point are lowered. E) None of the above. 18. A compound is found to have a molar mass of 598 g/mol. If 5.8 mg of the compound is dissolved in enough water to make 175 ml of solution at 25 C, what is the osmotic pressure of the resulting solution? A).42 mmhg B) 6.6 mmhg C) 5.01 mmhg D) 5.99 mmhg E) 8.6 mmhg 19. Identify the solute with the highest van't Hoff factor. A) nonelectrolyte B) NaCl C) MgSO4 D) MgCl2 E) FeCl 20. Fluids used for an intravenous transfusion must be with bodily fluids. A) isosmotic B) hyperosmotic C) hyposmotic D) neosmotic E) magnosmotic 21. Define smoke as a colloid. A) a liquid dispersed in a gas B) a solid dispersed in a gas C) a liquid dispersed in a liquid D) a liquid dispersed in a solid E) a solid dispersed in a liquid 4
22. Vanadium crystallizes in a body centered cubic structure and has an atomic radius of 11 pm. Determine the density of vanadium, if the edge length of a bcc structure is 4r/. A).06 g/cm B) 12.2 g/cm C) 6.11 g/cm D) 2.77 g/cm E) 8.46 g/cm 2. Which of the following is not a covalent network solid? a) silicon carbide b) quartz c) zinc d) diamond e) graphite 24. The metal chromium crystallizes in a body centered cubic lattice. If the density of chromium is 7.14 g/cm, what is the unit cell edge length? a) 20 pm b) 289 pm c) 77.0 pm d) 77.5 pm e) 61.1 pm 25. Why does hydrogen fluoride has an unusually high normal boiling point compared to the other hydrogen halides? a) The H F bond in hydrogen fluoride is very strong. b) Hydrogen fluoride is capable of forming hydrogen bonds. c) Hydrogen fluoride has very strong London dispersion forces. d) Hydrogen fluoride is ionic. e) Hydrogen fluoride is covalent. 26. For a particular liquid, raising its temperature from 298 K to 18 K causes its vapor pressure to double. What is the enthalpy of vaporization of this liquid? (R = 8.14 J/(K mol)) a) 115 kj/mol b) 288 kj/mol c) 27. kj/mol d) 2.5 kj/mol e) 270 kj/mol 5
27. You have two salt solutions A and B; Solution A has a higher boiling point than solution B. Which of the solutions (if any) has a HIGHER melting point? a) Solution A b) Solution B c) You need to know the salt concentrations to answer this d) They have equal melting point e) I have no Idea 28. The phase diagram for Kr is below. If you move from the conditions at point A to those at point D, which of the following is true? a) the Kr is warmed and vaporizes b) the Kr is cooled and vaporizes c) the Kr is cooled and freezes d) the Kr is warmed and melts e) the Kr does not change temperature but sublimes 29. Which type of solid is expected to have the lowest melting point? a) network b) ionic c) molecular d) metallic e) no such solids exist 0. Which way of expressing concentration is used to relate the vapor pressure of a solution to the amount of nonvolatile solute dissolved in the solution? a) molarity b) mole fraction c) molality d) mass percent e) osmotic pressure END 6
Important equations and formulas RT Root mean square velocity of a gas; u = M P2 Clausius Clapeyron equation; ln P = ΔHvap 1 1-1 R T1 T2 Volume of a sphere = 4 r 1/2 π, Volume of a cube = l The edge length of the cubic unit cells l= 2r (for a simple cubic cell) l = 4r (for a body centered cubic cell) l =2 2r or simply l= 8 r (for a face centered cubic cell) Metric and other unit conversions 1 m = 1.0x10 2 cm 1 g = 1.0 x10 mg 1 Kg = 1.0 x10 g 1 m =1.0x10 9 nm 1 KJ = 1.0 x10 J 1 m =1.0x10 12 pm 1 cm = 1.0x10 10 pm 1 atm=760 mmhg (torr) 1 atm=1.0125x10 5 Pa Osmotic pressure; π = MRT ΔT b = K b m or ΔT b = ik b m ΔT f = K f m or ΔT f = ik f m 7