Chem 130
Fall 99
EXAM 4
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?
a) ICl4-1
b) NO2+1
c) SeF4
d) SO3
e) I3-1
d) SO3
e) I3-1
2. Which of the following molecules or ions is polar?
a) ICl4-1
b) NO2+1
c) SeF4
3. Which of the following molecules or ions exhibits sp3d hybridization?
a) ICl4-1
b) NO2+1
c) SeF4
d) SO3
e) I3-1
d) SO3
e) I3-1
4. Which of the following molecules or ions exhibits resonance?
a) ICl4-1
b) NO2+1
c) SeF4
5. Which of the following molecules or ions has a trigonal bipyramidal electron pair arrangement?
a) ICl4-1
b) NO2+1
c) SeF4
d) SO3
e) I3-1
d) 120o
e) 72o
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) 90o
b) 180o
c) 109.5o
8. Three molecular shapes that are possible with sp3 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
9. Which one of the following molecules exhibits Hydrogen bonding?
a) CH3F
b) PH3
c) NF3
d) OF2
e) H2O2
10. The statement(s) which describe the bonding in PH3 is(are):
3. sp2 hybridization
4. polar molecule
1. trigonal planar
2. one lone pair on P
a) 1 only
b) 1,2, and 4 only
c) 2,3, and 4 only
d) 2 and 4 only
e) 1 and 3 only
11. The approximate O-N-O bond angle in the nitrite cation, NO2+1, is:
a) 60o
b) 90o
c) 109o
d) 120o
e) 180o
12. The molecule AX2, in which A is the central atom, is polar and obeys the rule of 8; therefore,
a) A has no lone pairs
b) A has one lone pair
c) A has two lone pairs
d) A has three lone pairs
e) A has four bonding pairs
13. Which of the following indicates the existence of strong intermolecular forces of attraction in a liquid?
a) a very low boiling point
b) a very low vapor pressure
c) a very low crirical temperature
d) a very low viscosity
e) a very low heat of vaporization
14. Which of the following substances likely has the highest critical temperature?
a) CH3NH2
b) CH3Cl
c) CCl4
d) CO2
e) C3H8
15. Which of the following ionic compounds would you expect to have the lowest melting point?
a) KI
b) KF
c) NaI
d) NaF
16. Which of the following phase changes is(are) exothermic?
a) vaporization only
b) sublimation only
c) condensation only
d) melting
e) both b and c
17. When a gas undergoes a phase change to a solid, the process is called:
a) sublimation
b) vaporization
c) solidification
d) deposition
e) condensation
e) RbI
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 SiH2F2?
I. dipole-dipole
a) II only
II. London Forces III. hydrogen bonding
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 20oC is warmed to 100oC and then vaporizes to
steam at 100oC. ( ∆Hvap = 40.66 kJ/mol...sp.ht. = 4.184 J/go)
a) 18.8 kJ
b) 129.8 kJ
c) 16.7 kJ
d) 112.9 kJ
e) none of these
22. Which of the following properties is characteristic of substances with a low critical point?
a) high molecular weights
b) high polarity
c) high vapor pressures
d) high heats of vaporization
e) none of these
23. Which bonding interaction best describes the intermolecular forces in carbon disulfide, CS2?
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, H2C2O4 . 2H2O, that is required to prepare
250.0 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
25. What is the mole fraction of methanol, CH3OH, in an ethanol, C2H5OH, 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
b) the molarity of the solution
c) the molecular weight of the solvent
d) the molecular weight of the solute
e) the mole fraction of the solute
27. The vapor pressures of xylene and toluene at 20oC 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 0.93oC. What is the molecular weight of the unknown. kb for water is 0.512oC/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, C6H12O6, in 500.0 grams of water?
a) 0.400
b) 0.200
c) 0.360
d) 0.720
e) 0.800
30. 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) Na3P
b) KNO3
c) CO2
d) MgCl2
e) (NH4)2SO4
31. At body temperature of 37oC, what is the osmotic pressure of a physiological solution of glucose
(a nonelectrolyte) with a concentration of 0.268 M. (R = 0.0821 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 MgF2 solution? (kf for water = 1.86oC/m)
(assume complete ionization.)
a) -3.72oC
b) +3.72oC
c) -5.58oC
d) -11.2oC
e) +5.58oC
33. For a 0.01 m solution of (NH4)3PO3 , the van't Hoff factor, i, would be approximately:
a) 6
b) 2
c) 3
d) 4
e) 8