EXAM 5 (Optional)
NAME_____KEY – Answers highlighted
CHEM 1211 VSU
Dr. Gosnell
Dec. 5, 2005
1. How many sigma (σ) bonds and pi (π) bonds are in acetic acid?
O
H
H
a) six σ and one π
d) eight σ and zero π
C
C
O
H
H
b) six σ and two π
e) eight σ and one π
c) seven σ and one π
2. To form a set of sp3d2 hybrid atomic orbitals, what set of pure atomic orbitals must be mixed?
a) one s, one p, and one d
c) one s, three p, and two d
b) one s, three p, and one d
d) two s, six p, and two d
e) two s, six p, and four d
3. What is the hybridization of the carbon atom in methane, CH4?
b) sp2
a) sp
c) sp3
d) sp3d
e) sp3d2
4. What is the molecular geometry around a central atom that is sp hybridized and no lone electronpairs?
a) bent
b) linear c) trigonal-planar d) trigonal-pyramidal e) trigonal-bipyramidal
5. What is the molecular geometry around a central atom that is sp3d hybridized and has three sigma
bonds and two lone electron-pairs?
a) linear
b) trigonal-pyramidal
c) trigonal-planar
d) tetrahedral
e) T-shaped
6. At constant temperature, 14.0 L of O2 at 0.882 atm is compressed to 1.75 L. What is the final pressure
of O2? Use P1V1 = P2V2 and solve for P2
P2 
(0.882atm)(14.0 L)
 7.06atm
1.75 L
a) 0.111 atm
b) 0.142 atm
c) 7.06 atm
d) 21.6 atm
e) 27.8 atm
7. If the volume of a confined gas is quadrupled while its temperature remains constant, what change
will be observed? P and V are inversely proportional.
a) The pressure of the gas will decrease to 1/4 its original value.
b) The pressure of the gas will quadruple.
c) The density of the gas will decrease to 1/2 its original value.
d) The average velocity of the molecules will quadruple.
e) The average velocity of the molecules will double.
8. The lid is tightly sealed on a rigid flask containing 3.50 L H2 at 17 °C and 0.913 atm. If the flask is
heated to 71 °C, what is the pressure in the flask? Temps must be in Kelvin
T1 P1

T2 P2
P2 
solve for P2
a) 0.770 atm
b) 1.08 atm
P1T2 (0.912atm)(344 LK )

 1.08atm
T1
290 K
c) 2.95 atm
d) 3.81 atm
e) 13.3 atm
9. Avogadro’s hypothesis states that equal volumes of gases under the same conditions of temperature
and pressure have equal ________.
a) densities
b) particle velocities
c) molar masses d) numbers of particles
e) masses
10. Which of the following relationships are true for gases?
I. The number of moles of a gas is directly proportional to its volume (at constant pressure).
II. The pressure of a gas is inversely proportional to its temperature in kelvins (at constant
volume).
III. The volume of a gas is directly proportional to its pressure (at constant temperature).
a) I only
b) II only
c) III only
d) I and II
e) II and III
11. The pressure in a 20.0 L flask is 0.512 atm at 72 °C. How many moles of gas are in the flask? (R =
0.08206 L·atm/mol·K)
PV=nRT solve for n, temp must be in K
a) 0.0297 mol
b) 0.142 mol
n
(0.512atm)( 20.0 L0
PV

 0.362mol
RT (0.08206 L  atm / K  mol )(345 K )
c) 0.276 mol
d) 0.362 mol
e) 1.73 mol
12. What volume is occupied by 8.50 g C2H2 at STP (standard temperature and pressure)? (R = 0.08206
L·atm/mol·K)
Calculate moles = 8.50g(1mol/26g)=0.327mol
Recall 1 mole at STP occupies 22.4L OR use PV=nRT and put in the right temp and pressure for STP
22.4 L
x

1mol 0.327mol
a) 0.670 L
solve for x
b) 7.31 L
c) 7.98 L
d) 68.7 L
e) 191 L
13. A mixture of He and O2 is placed in a 4.00 L flask at 32 C. The partial pressure of the He is 2.7 atm
and the partial pressure of the O2 is 1.4 atm. What is the mole fraction of O2?
Ptotal= 2.7atm + 1.4 atm = 4.1 atm
Poxygen  X oxygen PTotal
solve for Xoxygen=1.4atm/4.1atm=.341
a) 0.224
b) 0.341
c) 0.481
d) 0.518
e) 0.659
14. Convert 357 mm Hg to atmospheres.
a) 0.357 atm
b) 0.470 atm
357mmHg
 .470atm
760mmHg / atm
d) 2.71 × 105 atm
c) 2.13 atm
15. Which of the following statements concerning gas pressure are correct?
I. Gas pressure arises from collisions of gas molecules with the walls of the container holding the gas.
II. Increasing the number of gas molecules within a container increases the number of collisions with
the walls of the container, thereby increasing the gas pressure.
III.As the temperature of a gas increases, gas molecules exert more force on the walls of their container.
a) I only
b) II only
c) III only
d) I, II, and III
16. Which one of the following substances will exhibit dipole-dipole intermolecular forces?
Look for one that’s polar.
a) C2H4
b) SO2
c) CO2
d) F2
e) Ar
17. What intermolecular force or bond is primarily responsible for the solubility of KCl in water?
KCl is an ionic compound. Water is a dipole (it’s polar)
a) ion-dipole force
d) covalent bonding
b) dipole-dipole force
e) hydrogen bonding
c) ionic bonding
18. Which intermolecular force or bond is responsible for the density of ice being less than that of liquid
water?
a) London dispersion forces
d) covalent bonding
b) hydrogen bonding
c) ionic bonding
e) dipole/induced dipole forces
19. What is the dominant intermolecular force or bond that must be overcome in converting CH3OH from
a liquid to a gas?
OH bond here is just like the OH bond in water and lets it H-bond,.
a) London dispersion force
b) hydrogen bonding
c) dipole-dipole force
d) covalent bonding
20. The bond order of a molecule containing equal numbers of bonding and antibonding electrons is ___?
a. 0
b. 1
c. 2
d. 3
e. 1/2
21. According to molecular orbital theory, overlap of two s atomic orbitals produces ___.
a.
b.
c.
d.
e.
one bonding molecular orbital and one hybrid orbital
two bonding molecular orbitals
two bonding molecular orbitals and two antibonding molecular orbitals
two bonding molecular orbitals and one antibonding molecular orbital
one bonding molecular orbital and one antibonding molecular orbital
22. STP refers to _____.
a. 298 K and 1 atm
b. 273 K and 1 atm
c. 298 K and 1 torr
d. 273 K and 1 Pa
23. Pressure of a gas is defined as
a. the force per unit volume
c. the force per unit area
b. the pounds per unit density
d. Joules per mole of molecular collisions
24. Which gas law relates temperature and volume at constant pressure and number of moles?
a. Boyle’s
b. Charles’
c. Avogadro’s
d. Avocado’s
e. Dalton’s
25. Which gas law relates pressure and volume at constant temperature and number of moles?
a. Boyle’s
b. Charles’
c. Avogadro’s
d. Avocado’s
e. Dalton’s
26. Which gas law relates moles and volume at constant pressure and temperature?
a. Boyle’s
b. Charles’
c. Avogadro’s
d. Avocado’s
e. Dalton’s
27. Which gas law applies to partial pressures in a mixture of gases?
a. Boyle’s
b. Charles’
c. Avogadro’s
d. Avocado’s
e. Dalton’s
28. A molecular orbital designated * is a _______ MO formed by mathematical “mixing” of _____.
a) bonding; an s orbital and a p orbital
c) anitbonding; two s orbitals
b) bonding; two p orbitals
d) antibonding; two p orbitals
29. Which orbital overlap is NOT a sigma bond?
a)
sigma
b)
c}
d)
e) none, they are all
30. Which is used to measure air pressure?
a) pedometer
b) torrometer
c) barometer
d) chronometer
31. When water is a solvent, we say the solute is _______.
a) hydrated
b) hydrogenated
c) wet
d) solventated
e) aqauatated
32. What causes an induced (transient) dipole? London dispersion forces have these.
a)
b)
c)
d)
distortion of the electron cloud by another molecule
hydrogen bonding with water
atoms of different electronegativities are bonded covalently
the surrounding of an ion, like Na+, with water
33. Which is the weakest intermolecular force?
a) dipole-dipole
b) ion-dipole
c) hydrogen bonding
d) London dispersion forces
Bonus
34. Using the diagram below there are _____ bonding electrons and _____ antibonding electrons for
F2 and the bond order is ____.
Fill in with a total of 18 electrons. Use the middle set of orbitals since these are the molecular
orbitals. Put 2 electrons in each box. Every pair of MO’s connected by dashed lines is a
bonding(bottom) and antibonding (upper) pair of orbitals. You end up with 10 electrons in bonding
orbitals and 8 in antibonding. This gives a bond order of 1.
Answers are not correct below. Should be 10,8,1. If you took this test then you will get 3 more
points.
a) 8; 8; 0
35. I am glad this test is over.
a) True
b) False
b) 6; 8; 1
c) 8; 6; 1
d) 7; 7 ; 0