Chapter 10: Gases
Zumdahl Practice Questions (Answers at end of document)
p. 231: 21abc, 27, 29, 33, 45, 55, 57, 61, 63ab, 65
21.
Freon-12 (CF2Cl2) is commonly used as the refrigerant in central home air conditioners. The
system is initially charged to a pressure of 4.8 atm. Express this pressure in each of the
following units.
(a) mm Hg
(b) torr
(c) Pa
27.
An aerosol can contains 400. mL of compressed gas at 5.20 atm pressure. When the gas is
sprayed into a large plastic bag, the bag inflates to a volume of 2.14 L What is the pressure of
gas inside the plastic bag? Assume temperature is constant.
29.
If 0.500 mol of nitrogen gas occupies a volume of 11.2 L at 0°C, what volume will 2.00 mol of
nitrogen occupy at the same temperature and pressure?
33.
The steel reaction vessel of a bomb calorimeter, which has a volume of 75.0 mL, is charged with
oxygen gas to a pressure of 145 atm at 22°C. Calculate the moles of oxygen in the reaction
vessel.
45.
What mass of helium is required to fill a 1.5-L balloon at STP?
55.
A gas consisting of only carbon and hydrogen has an empirical formula of CH2. The gas has a
density of 1.65g/L at 27°C and 734 torr. Determine the molar mass and molecular formula of
the gas.
61.
Consider the flasks diagrammed below. What are the final partial pressures of H2 and N2 after
the stopcock between the two flasks is opened? (Assume the final volume is 3.00L) What is the
total pressure in torr? [Initial pressure and volume of H2 is 475 torr and 2.00L; initial pressure
and volume of N2 is 0.200 atm and 1.00 L]
63.
The partial pressure of CH4 (g) is 0.175 atm and that of O2 (g) is 0.250 atm in a mixture of the
two gases.
(a) What is the mole fraction of each gas in the mixture?
(b) If the mixture occupies a volume of 10.5 L at 65°C, calculate the total number of moles of gas
in the mixture.
65.
A sample of nitrogen gas was collected over water at 20°C and a total pressure of 1.00 atm. A
total volume of 2.50 x 102 mL was collected. What mass of nitrogen was collected? (At 20°C the
vapor pressure of water is 17.5 torr.)
Answers:
21.
(a) 3.6 x 103 mmHg
(b) 3.6 x 103 torr
(c) 4.9 x 105 Pa
27.
0.972 atm
29.
44.8 L
33.
0.449 mol
45.
0.27 g
55.
42.1 g/mol, C3H6
57.
SiCl4, D = 5.77 g/L
SiHCl3, D = 4.60 g/L
61.
PH2 = 317 torr
PN2 = 50.7 torr
Ptotal = 368 torr
63.
(a)
XCH4 = 0.412
XO2 = 0.588
(b)
65.
0.286 g
0.161 mol