PLEASE DO NOT MARK ON THE EXAM. ALL ANSWERS SHOULD BE INDICATED ON THE ANSWER SHEET. c) SeF 4

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1 Chem 130 EXAM 4 Fall 99 PLEASE DO NOT MARK ON THE EXAM. ALL ANSWERS SHOULD BE INDICATED ON THE ANSWER SHEET QUESTIONS 1-5 MAY HAVE MORE THAN ONE POSSIBLE ANSWER CIRCLE ALL CORRECT RESPONSES TO EACH QUESTION 1. Which of the following molecules or ions has a linear molecular shape? 2. Which of the following molecules or ions is polar? 3. Which of the following molecules or ions exhibits sp 3 d hybridization? 4. Which of the following molecules or ions exhibits resonance? 5. Which of the following molecules or ions has a trigonal bipyramidal electron pair arrangement? 6. When a carbon atom has sp hybridization, it has: a) four σ bonds b) three σ bonds and one π bond c) two σ bonds and two π bonds d) one σ bonds and three π bonds e) four π bonds 7. The octahedral bond angle is approximately a) 90 o b) 180 o c) o d) 120 o e) 72 o 8. Three molecular shapes that are possible with sp 3 hybridization are a) 'see-saw', T-shape, linear b) octahedral, square pyramid, square planar c) trigonal planar, angular, T-shape d) tetrahedral, trigonal pyramid, angular e) none of these

2 9. Which one of the following molecules exhibits Hydrogen bonding? a) CH 3 F b) PH 3 c) NF 3 d) OF 2 e) H 2 O The statement(s) which describe the bonding in PH 3 is(are): 1. trigonal planar 3. sp 2 hybridization 2. one lone pair on P 4. polar molecule a) 1 only d) 2 and 4 only b) 1,2, and 4 only e) 1 and 3 only c) 2,3, and 4 only 11. The approximate O-N-O bond angle in the nitrite cation, NO 2, is: a) 60 o b) 90 o c) 109 o d) 120 o e) 180 o 12. The molecule AX 2, in which A is the central atom, is polar and obeys the rule of 8; therefore, a) A has no lone pairs d) A has three lone pairs b) A has one lone pair e) A has four bonding pairs c) A has two lone pairs 13. Which of the following indicates the existence of strong intermolecular forces of attraction in a liquid? a) a very low boiling point d) a very low viscosity b) a very low vapor pressure e) a very low heat of vaporization c) a very low crirical temperature 14. Which of the following substances likely has the highest critical temperature? a) CH 3 NH 2 b) CH 3 Cl c) CCl 4 d) CO 2 e) C 3 H Which of the following ionic compounds would you expect to have the lowest melting point? a) KI b) KF c) NaI d) NaF e) RbI 16. Which of the following phase changes is(are) exothermic? a) vaporization only d) melting b) sublimation only e) both b and c c) condensation only 17. When a gas undergoes a phase change to a solid, the process is called: a) sublimation d) deposition b) vaporization e) condensation c) solidification

3 18. In the accompanying phase diagram, a change from point A to point B corresponds to: a) vaporization b) condensation c) sublimation d) deposition e) freezing B A 19. The normal boiling point of a liquid is: a) the only temperature at which there can be an equilibrium between the liquid and gas states. b) the temperature above which the substance cannot exist as a liquid regardless of pressure. c) the temperature at which gas molecules have more kinetic energy than molecules in the liquid. d) the temperature at which vapor pressure equals 760 mm Hg. e) none of these. 20. Which of the following are intermolecular forces in SiH 2 F 2? I. dipole-dipole II. London Forces III. hydrogen bonding a) II only b) I and II c) I, II and III d) II and III e) I and III 21. Calculate the energy absorbed when 50 grams of water at 20 o C is warmed to 100 o C and then vaporizes to steam at 100 o C. ( H vap = kj/mol...sp.ht. = J/g o ) a) 18.8 kj b) kj c) 16.7 kj d) kj e) none of these 22. Which of the following properties is characteristic of substances with a low critical point? a) high molecular weights d) high heats of vaporization b) high polarity e) none of these c) high vapor pressures 23. Which bonding interaction best describes the intermolecular forces in carbon disulfide, CS 2? a) primarily London forces b) covalent bonding to form a network solid c) ionic bonding d) metallic bonding e) primarily dipole-dipole interactions 24. Calculate the number of grams of oxalic acid dihydrate, H 2 C 2 O 4. 2H 2 O, that is required to prepare ml of 1.25 M solution. a) 28.1 g b) 43.6 g c) 90.0 g d) 39.4 g e) none of these

4 25. What is the mole fraction of methanol, CH 3 OH, in an ethanol, C 2 H 5 OH, solution that is 60% ethanol by mass? a) 0.40 b) 0.46 c) 0.49 d) 0.54 e) none of these 26. For a two-component system, one can calculate the mole fraction of the solvent directly, given only: a) the density of the solution d) the molecular weight of the solute b) the molarity of the solution e) the mole fraction of the solute c) the molecular weight of the solvent 27. The vapor pressures of xylene and toluene at 20 o C are 50 mm and 80 mm respectively. What is the vapor pressure of the mixture containing 7.0 mol xylene and 3.0 mol toluene. (note: they both have a vapor pressure) a) 130 mm b) 11 mm c) 71 mm d) 59 mm e) none of these 28. When 20.0 grams of an unknown nonelectrolyte were dissolved in 150 grams of water, the boiling point was raised by 0.93 o C. What is the molecular weight of the unknown. k b for water is o C/m a) 63.0 b) 73.4 c) 13.6 d) 41.3 e) none of these 29. What is the molality of a solution that contains 36.0 grams of glucose, C 6 H 12 O 6, in grams of water? a) b) c) d) e) Solutions are made which contain 0.10 moles of each of the following substances in 1000 g. water. Choose the compound whose solution will have the lowest freezing point. a) Na 3 P b) KNO 3 c) CO 2 d) MgCl 2 e) (NH 4 ) 2 SO At body temperature of 37 o C, what is the osmotic pressure of a physiological solution of glucose (a nonelectrolyte) with a concentration of M. (R = l-atm/mol-k) a) 16 atm b) 9.50 atm c) 8.14 atm d) 6.82 atm e) none of these 32. What is the approximate freezing point of an aqueous 2.00 molal MgF 2 solution? (k f for water = 1.86 o C/m) (assume complete ionization.) a) o C b) o C c) o C d) 1.2 o C e) o C 33. For a 0.01 m solution of (NH 4 ) 3 PO 3, the van't Hoff factor, i, would be approximately: a) 6 b) 2 c) 3 d) 4 e) 8

Chem 124 Exam 1 Spring 2016 Version 1 Name

Chem 124 Exam 1 Spring 2016 Version 1 Name TOTAL POINTS - 116 MULTIPLE CHOICE 1.4 POINTS EACH 1) A molecule containing a central atom with sp 3 hybridization has a(n) electron geometry. A) linear B) tetrahedral