Name____________________________________________
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Chapter 5 Review
Complete the following:
The __1__ of the particles in a gas with the walls of the container results in gas __2__. The
total pressure in a mixture of gases is equal to the sum of the __3__ of each gas present. This is
known as __4__ law of partial pressures.
The pressure and volume of a fixed mass of gas are __5__ related. If one decreases, the
other __6__. This relationship is known as __7__ law. The __8__ of a fixed volume of a gas is
directly related to its __9__ temperature. The __10__ of a gas at constant pressure is __11__
related to its Kelvin temperature. This is known as __12__ law.
These three separate gas laws can be written as a single expression called the __13__.
Another expression is the ideal gas law, __14__, where n = __15__. The letter R is the __16__
constant, and is equal to __17__.
1. collisions
10. volume
2. pressure
11. directly
3. partial pressures
12. Charles’
4. Dalton’s
13. combined gas law
5. inversely
14. PV = nRT
6. increases
15. number of moles
7. Boyle’s
16. universal gas
8. pressure
17. 0.0821 L atm/molK or 8.31 L kPa/molK
9. Kelvin
1. A gas is contained in a stretchable container and has a volume of 6.0 L. Determine the new
volume if the following changes occur. Assume temperature changes refer to Kelvin and
pressure refers to outside pressure.
a. pressure is doubled
3.0 L
b. temperature is doubled
12.0 L
c. pressure and temperature are both doubled
6.0 L
d. pressure is doubled and temperature is halved
1.5 L
e. pressure and temperature are both halved
6.0 L
2. Given 20.0 L of ammonia at 5ºC and 760 torr, determine its volume at 30ºC and 800. torr.
use combined gas law:
(760 torr)(20.0 L)
278 K
=
(800. torr)(V2)
303 K
V2 = 20.7 L
3. At 18ºC and 765 torr, 1.29 L of a gas weighs 2.71 g. Calculate the approximate molar mass
of the gas.
MM = gRT / PV
MM = (2.71 g)(0.0821 Latm/molK)(291 K)
(765/760 atm)(1.29 L)
MM = 49.9 g/mol
4. Compute the density of methane at 20.0ºC and 5.00 atm.
MM = gRT / PV → g/V = MM P / RT
g/V =
(5.00 atm)(16.05 g/mol)
(0.0821 Latm/molK)(293 K)
g/V = 3.34 g/L
5. How many grams of zinc must be dissolved in excess sulfuric acid in order to obtain 500. mL
of hydrogen at 20ºC and 770 torr? Zn(s) + H2SO4 → ZnSO4 + H2(g)
nH2 =
(770/760 atm)(0.500 L)
(0.0821 Latm/molK)(293 K)
0.021 mol H2 x
1 mol Zn
1 mol H2
=
x
0.021 mol H2
65.39 g Zn
1 mol Zn
=
1.4 g Zn
6. A container is divided into two separate chambers, one having a volume of 2.125 L filled with
SO2 at 0.750 atm and the other having a 1.500 L volume filled with O2 at 0.500 atm; both gases
are at 80ºC. The divider between the chambers is removed. What are the mole fractions, the
total pressure, and the partial pressures?
use Boyle’s Law to find new partial pressures:
PSO2 (3.625 L) = (0.750 atm)(2.125 L)
PSO2 = 0.440 atm
Ptot = 0.647 atm
PO2 (3.625 L) = (0.500 atm)(1.500 L)
PO2 = 0.207 atm
mole fractions:
SO2 = 0.440 = 0.680
0.647
O2 = 1 – 0.680 = 0.320
7. Compute the relative rates of effusion of H2 and CO2.
use Graham’s Law:
rateH2
=
rateCO2
44.01 g/mol
2.02 g/mol
=
4.67
H2 effuses 4.67 x faster than CO2
8. One of the methods for estimating the temperature of the center of the sun is based on the
ideal gas law. If the center is assumed to consist of gases whose average molar mass is 2.0, and
if the density and pressure are 1.4 x 103 g/L and 1.3 x 109 atm, calculate the Kelvin temperature.
MM = gRT/PV
→
T = MM P V
gR
T =
(2.0 g/mol)(1.3 x 109 atm)(1.0 L)
(1.4 x 103 g)(0.0821 Latm/molK)
T = 2.3 x 107 K
9. An electronic vacuum tube was sealed off during manufacture at a pressure of 1.2 x 10-5 torr
at 27ºC. Its volume is 0.200 L. Compute the number of gas molecules remaining in the tube.
PV = nRT
→
n = PV / RT = (1.2 x 10-5/760 atm)(0.200 L)
(0.0821 Latm/molK)(300 K)
n = 1.3 x 10-10 mol x 6.02 x 1023 molecules
1 mol
= 7.7 x 1013 molecules