Part III Chapters 5, 10 and 11
1. The value of Ho for the following reaction is -6535 kJ. How many kJ of heat will be evolved
during the combustion of 16.0 g of C6H6(l)?
The heats of formation for CO2 and H2O are -393.5 kJ/mol and -286 kJ/mol respectively.
2C6H6(l) + 15O2 (g) ----------> 12CO2 (g) + 6H2O(l)
a) 1.34 X 103
b) 5.23 X 104
c) 670
d) 2.68 X 103
2. When 72 g of a metal at 97.0oC is added to 100 g of water at 25.0oC, the final temperature is
found to be 29.1oC. What is the heat capacity per gram of the metal?
(Heat capacity of H2O = 4.184 J/g oC)
a) 0.46 J/g oC
b) 2.8 J/g oC
c) 0.35 J/g oC
ANS = c
d) 2.0 J/g oC
3. Substance
SO2 (g)
SO3 (g)
SO2Cl2 (g)
H2SO4 (l)
H2O (l)
Hfo ( kJ/mol)
-297
-396
-364
-814
-286
The value of Ho for the following reaction is -62 kJ. What is the values of Hfo (in kJ/mol) for
HCl (g)?
SO2Cl2 (g) + 2H2O (l) ---------> H2SO4 (l) + 2HCl (g)
a) -184
b) 60
c) -92
d) 30
4. Substance
H2O (l)
NO (g)
NO2 (g)
HNO3 (aq)
NH3 (g)
Hfo ( kJ/mol)
-286
90
34
-207
-46
Calculate the value of Ho (in kJ) for the following readtion.
4NH3 (g) + 5O2 (g) ---------> 4NO (g) + 6H2O (l)
a) -1172
b) -150
c) -1540
d) -1892
5. A 30.52 g chunk of metal having a specific heat of 0.185 J/g deg was heated to 95 oC. This
metal was immediately immersed in 50 mL of water at 25oC. Assume the density of water to
be 1.00 g/mL and the specific heat of water to be 4.184 J/g deg. The final temperature of the
water after equilibration is
a) 30.6 oC
b) 48.2 oC
c) 26.8 oC
ans = c
d) 60.0 oC
6. Arrange the gases Cl2, O2, F2, N2 in order of increasing average molecular speed at 25øC.
a) Cl2, F2, O2, N2
b) Cl2, O2, F2, N2
c) N2, F2, Cl2, O2
ans = a
d) Cl2, F2, N2, O2
7. At STP, the root-mean-square speed of CO2 is how many times that of SO2?
a) 2.001
b) 2.119
c) 1.000
ans = d
d) 1.206
e) 1.456
8. According to the kinetic-molecular theory, molecules of different gases at the same
temperature always have the same
a) molecular weight
b) pressure
ans = c
c) average kinetic energy
d) volume
9. A flask contains a mixture of two gases, A and B, at a total pressure of 2.6 atm. There are 2.0
moles of gas A and 5.0 moles of gas B in the flask. What is the partial pressure (in atm) of gas
A?
a) 9.1
b) 6.5
ans = d
c) 1.04
d) 0.74
10. Automobile air bags use the decomposition of sodium azide as their
source of gas for rapid inflation: 2NaN3(s) ---------> 2Na(s) + 3N2 (g). How many grams of
NaN3 are required to provide 40.0 L of N2 at 25oC and 763 mm Hg?
a) 1.64 g
b) 1.09 g
c) 160 g
ans = d
d) 71.1 g
e) 107 g
11. What is the pressure in a 12.2 L vessel that contains 2.34 g of carbon dioxide, 1.73 g of sulfur
dioxide, and 3.33 g of argon at 42øC?
a) 263 torr
b) 134 torr
c) 395 torr
ans = a
d) 116 torr
12. What is the molecular weight of a gas which has a density of 5.75 g/L at STP?
a) 3.90
b) 129
c) 141
ans = b
d) 578
13. Which one of the following substances has dispersion forces as its only intermolecular force?
a) CH3OH
b) NH3
c) H2S
ans = d
d) CH4
14. The intermolecular force(s) responsible for the fact that CH4 has the lowest boiling point in
the set CH4, SiH4, GeH4, SnH4 is/are
a) hydrogen bonding
b) dipole-dipole interactions
ans = c
c) London-dispersion forces
d) mainly hydrogen bonding but also dipole-dipole interactions
e) mainly London-dispersion forces but also dipole-dipole interactions
15. Molecules with hydrogen bonded to nitrogen, oxygen, or fluorine can exhibit hydrogen
bonding.
16. A 3.50 gram sample containing KClO3 and KCl was heated to decompose the KClO3 to KCl
and O2. The liberated oxygen was collected over water and at 27oC and 748 torr pressure and
the volume of oxygen collected was 360 mL. The vapor pressure of water at 27oC us 30 torr.
Balance the equation that describes this reaction and determine the mass percent of KClO3 in
the sample.
ans = 32.2%
17. A 2.82 gram sample of benzoic acid, C7H6O2, was burned in excess oxygen in a bomb
calorimeter to liberate CO2 (g) and H2O (l). The temperature increased from 25.2oCto
27.8oC. The bomb calorimeter was immersed in three liters of water. The heat capacity of
the calorimeter itself is 120 J/deg and the heat capacity of water is 4.184 J/g deg. Assume the
density of water is 1.0 g/mL. Calculate the heat of formation for benzoic acid. The heats of
formation of CO2 (g) and H2O (l) can be found in problem 1 in this section.
18. A compound has the following properties:
Triple point temperature …… 10oC
Triple point pressure
…… 200 torr
Normal boiling point ………...200oC
Normal freezing point ……….15oC
Draw a phase diagram and label all points, lines and areas. According to your phase diagram,
what is the vapor pressure of this compound at 100oC?