Topics – Gases
•
Gas Laws
o Boyles Law, PV = K or P1V1 = P2V2
o Charles Law, V/T = K or V1/T1 = V2/T2
o Gay-Lussac’s Law, P/T = K or P1/T1 = P2/T2
o Ideal Gas Law, PV = nRT where R = 0.0821 Latm/moleK
 An ideal gas is a substance that has no molecular volume and no intermolecular forces of
attraction.
•
Multiple Choice
1. Under which conditions does a real gas
minimize its intermolecular forces of attraction
and behave most like an ideal gas?
(1) at low temperatures and high pressures
(2) at low temperatures and low pressures
(3) at high temperatures and high pressures
(4) at high temperatures and low pressures
2. The volume of gas is 4.00 liters at 293 K and
constant pressure. For the volume of the gas to
become 3.00 liters, the Kelvin temperature must
be equal to
(1) 3.00 x 293
4.00
(3) 3.00 x 4.00
293
(2) 4.00 x 293
3.00
(4)
. 293 .
3.00 x 4.00
3. Which graph best represents the pressurevolume relationship for an ideal gas at constant
temperature?
4. A real gas behaves more like an ideal gas when
the gas molecules are
(1) close and have strong attractive forces
between them
(2) close and have weak attractive forces
between them
(3) far apart and have strong attractive forces
between them
(4) far apart and have weak attractive forces
between them
5. A gas occupies a volume of 40.0 milliliters at
20°C. If the volume is increased to 80.0
milliliters at constant pressure, the resulting
temperature will be equal to
(1) 20°C x 80.0 mL
40.0 mL
(3) 293 K x 80.0 mL
40.0 mL
(2) 20°C x 40.0 mL
80.0 mL
40.0 mL
(4) 293 K x 80.0 mL
6. At constant temperature, the relationship
between the volume (V) of a given mass of gas
and its pressure (P) is
(1) V = kP
(2) P = kV
(3) PV = k
(4) V/P = k
7. A mixture of gases has a total pressure of 2000
torr. The mixture contains 8 moles of nitrogen
gas and 2 moles of oxygen gas. What pressure is
exerted by the oxygen gas molecules?
(1) 200 torr
(2) 400 torr
(3) 2000 torr
(4) 4000 torr
8. As the temperature of a given sample of a gas
decreases at constant pressure, the volume of the
gas
(1) decreases
(2) increases
(3) remains the same
9. The pressure on a 200 milliliter sample of CO2
(g) at constant temperature is increased from
600 torr to 1,200 torr. What is the new volume
of the gas?
(1) 100 mL
(2) 300 mL
(3) 400 mL
(4) 600 mL
10. What is the volume, in liters, of 576 grams of
SO2 gas at STP?
(1) 101 L
(2) 202 L
(3) 216 L
(4) 788 L
11. What is the total volume occupied by 132 grams
of CO2 (g) at 0°C and 1.0 atm of pressure?
(1) 22.4 L
(2) 33.6 L
(3) 44.8 L
(4) 67.2 L
12. At the same temperature and pressure, 1.0 liter
of CO (g) and 1.0 liter of CO2 (g) have
(1) equal masses and the same number of
molecules
(2) different masses and a different number of
molecules
(3) equal volumes and the same number of
molecules
(4) different volumes and a different number of
molecules
13. A volume of air is in a container whose volume
can be changed using a piston. As the piston
reduces the volume of the air, the number of gas
molecules
(1) decreases
(2) increases
(3) remains the same
14. What will be the new volume of a 1.00 mole
sample of a gas at STP if the pressure remains
constant and the Kelvin temperature is halved?
(1) 11.2 L
(2) 22.4 L
(3) 33.6 L
(4) 44.8 L
15. At the same temperature and pressure, which
sample contains the same number of moles of
particles as 1 liter of O2 (g)?
(1) 1 L Ne (g)
(2) 2 L N2 (g)
(3) 0.5 L SO2 (g)
(4) 1 L H2O (l)
16. A gas occupies a volume of 40.0 milliliters at 20
°C. If the volume reduced to 20.0 milliliters at
constant pressure, the resulting temperature
must be
(1) 10 °C
(2) 0 °C
(3) 313 °C
(4) –127 °C
17. Which graph shows the pressure-temperature
relationship expected for an ideal gas?
19. Which of the following represents standard
temperature and pressure?
(1) 760 torr and 0 K
(2) 1 torr and 0 K
(3) 760 torr and 0 °C
(4) 1 torr and 0 °C
20. The height of a mercury barometer on a day
when the pressure was 0.938 atm is
(1) 760 mm
(2) 712 mm
(3) 12 mm
(4) 772 mm
21. Which of the following represents Boyles’ law,
which is the pressure volume relationship of an
ideal gas?
(1)
(1) PV = k
(2) P/T = k
(3) V/T = k
(4) PV/T = k
22. Which of the following gases is most like an
ideal gas?
(1) He
(2) Ne
(2)
(3) Ar
(4) Xe
23. If the temperature of a gas is held constant and
the pressure doubles, the volume of the gas must
(1) double
(2) halve
(3) remain the same.
(3)
18. What is the temperature of 1.5 moles of a gas
that is confined in a 3.5 L flask at 760 torr of
pressure? R = 0.0821 L atm/mole K
(1) 0 °C
(2) –245 °C
(3) 28 °C
(4) 273 °C
24. If the volume of a flask remains constant and
the temperature is increased, what happens to
the pressure?
(1) It increases
(2) It decreases
(3) It remains the same.
CHM1
Review for Exam 10
Part D. Free response.
Directions: Provide written responses to the following questions, using complete
sentences when appropriate and showing all work for calculations.
25. (6 pts) Dr. VDS has recently synthesized a new uranium compound and needed to
determine the molecular weight in order to publish a paper. He determined that
13.4 grams occupied 1.0 L when this compound was in the gas phase at 273 K
and 1 atm presure. What was the molecular weight (g/mole) of this compound?
PV = nRT, R = 0.0821 L.atm/mole K
26. (5 pts) At STP a balloon has a volume of 4.0 L. What will the volume of the
balloon become at 25°C and a pressure of 0.95 atm?
27. (6 pts) Describe three properties of an ideal gas and explain how they would be
different for a real gas.
CHM1
Review for Exam 10
28. (5 pts) Base your answers to questions 31 and 32 on the following diagram, which
shows a piston confining a gas in a cylinder.
Using the set of axes provided, sketch the general relationship between the pressure
and the volume of an ideal gas at constant temperature.
Volume
Pressure
29. (5 pts) The gas volume in the cylinder is 6.2 milliliters and its pressure is 1.4
atmospheres. The piston is then pushed in until the gas volume is 3.1 milliliters
while the temperature remains constant. Calculate the pressure, in atmospheres,
after the change in volume. Show all work.
CHM1
Review for Exam 10
Answers
1. 4
2. 1
3. 4
4. 4
5. 3
6. 3
7. 2
8. 1
9. 1
10. 2
11. 4
12. 3
13. 3
14. 1
15. 1
16. 4
17. 1
18. 2
19. 3
20. 2
21. 1
22. 1
23. 2
24. 1
25. 300 g/mole
26. 4.6 L
27. An ideal gas has no molecular volume and as a result is infinitely compressible. Real
gases have molecular volumes and become liquids or solids under conditions of high
pressure. An ideal gas has no intermolecular forces of attraction and collisions are
totally elastic. Real gases have intermolecular forces of attraction (London dispersion
forces, dipole-dipole, Van der Waals forces) which cause their collisions to be
somewhat inelastic, and causing the real gas to become a liquid or solid at high
pressure and low temperatures.
28.
29. 2.8 atm
Volume