Review: Chapter 13 Gas Laws
(p 1 of 2)
1.
Which of the following is not a proper pressure unit?
a.
torr
b.
atmosphere
c.
lb/in2
d. all are pressure units
2.
The vapor pressure over a beaker of hot water is
measured as 656 torr. What is this pressure in
atmospheres?
a. 1.16 atm
b. 0.863 atm
c. 0.756 atm
d. 0.500 atm
3.
Which one of the following relationships concerning the
pressure and volume of a fixed mass of gas at constant
temperature is incorrect?
a.
P1V 1 = k
b. P1V1 = P2V2
c.
P α 1/V
d. P = kV
4.
A gas sample with a volume of 800.0 mL and a pressure of
1.00 atm is reduced in volume to 250.0 mL at constant
temperature. The new pressure of the gas is
a. 0.100 atm
b. 0.313 atm
c. 1.50 atm
d. 3.20 atm
5.
Which relationship concerning the pressure and
temperature of a fixed mass of gas at constant volume is
correct?
a. P1T1 = P2T2
b.
P = kT
c.
P+T=k
d.
PT = k
6.
7.
If a 1.00 L sample of CO2 at 27oC is cooled to 15oC at
constant atmospheric pressure of 1.00 atm, what is the
new volume of the gas?
a.
1.50 L
b.
1.33 L
c.
1.04 L
d.
0.960 L
In the stratosphere, ozone, O3, absorbs high energy UV
radiation and breaks down into diatomic oxygen gas:
2O3 + lightuv

3O2
If 1.00 L of O3 is illuminated with UV radiation at
constant pressure and temperature, what volume of O2
will form?
a.
3.00 L
b.
2.00 L
c.
1.50 L
d.
1.00 L
8.
Carbon monoxide is a toxic gas that competes very
successfully for active sites on hemoglobin, and can thus
cause suffocation. If 22.0 g of pure CO is in a 20.0 L
container at a temperature of 25oC, what pressure (atm)
does the gas exert?
a. 0.961 atm
b.
0.881 atm
c.
1.04 atm
d.
1.68 atm
9.
It is increasingly recognized that the key to smog
reduction is the control of NO emissions from vehicles.
If 50.0 ml of the NO emitted from an exhaust pipe at
200oC exerts a pressure of 1.80 atm, what pressure will
it exert when it is transferred into a 100.0 mL container
and cooled to 25oC?
a. 2.14 atm
b.
0.567 atm
c.
1.95 atm
d.
0.877 atm
10. A sample of water is decomposed electrolytically and
produces a mixture of hydrogen and oxygen gas. If the
mixture of the two gases exerts a total pressure of 620
torr, what is the partial pressure of the hydrogen?
a. 207 torr
b.
310 torr
c.
413 torr
d.
465 torr
11.
Which of the following is least important in determining
the physical behavior of a gas?
a. pressure
b. temperature
c. volume
d. chemical composition
12. A model that explains observed behavior, such as the
physical behavior of gases, is referred to as a(n)
a.
hypothesis
b.
law
c.
observation
d.
theory
13.
All of the following are postulates of the kinetic
molecular theory of gases except
a. The volume of gas particles is negligible compared to
the volume of the container.
b. Attraction and repulsion of gas particles is
negligible.
c. The average kinetic energy of the gas particles is
proportional to the temperature in Kelvin.
d. Collisions of gas particles with the container walls
are inelastic.
14.
According to kinetic molecular theory, if we heat a gas
sample that is sealed in a rigid container, the particles
move ____ because they have a higher _____ energy,
causing them to collide more frequently with the walls of
the container and thus causing an increase in _____.
a. faster ; potential ; volume
b. faster ; kinetic ; pressure
c. slower ; kinetic ; volume
d. slower ; kinetic ; pressure
Review: Chapter 13 Gas Laws
15.
(p 2 of 2)
Consider the following reactions: 2C2H2(g) + 5O2(g)  4CO2(g) + 2H2O(g)
How many liters of O2 are needed to completely react with 5.2 liters of acetylene (C2H2)?
a. 13 L
b. 10.4 L
c. 5.2 L
d. 5.0 L
ANSWERS
1. Choice d properly explains that all are used as pressure units.
2. Choice b provides the correct value, which is easily obtained by dimensional analysis: 656 torr * 1atm/760torr = 0.863
3. Choice d incorrectly states that pressure and volume are proportional. The first three choices correctly state the inverse relationship
between pressure and volume of a gas: if the volume of a fixed mass of gas is decreased at constant temperature, the pressure increases.
4. Choice d correctly gives the response arrived at using Boyle’s Law:
P1V1 = P2V2 = (1.00 atm) (800.0 ml) = (P2) (250.0 ml) ; P2 = 3.20 atm
5. Choice b reflects the direct proportionality between pressure and temperature of a gas. If the temperature of a gas is increased at
constant mass and volume, the pressure will rise proportionately.
6. Choice d is derrived by using Charles’s Law:
V1/T1= V2/T2 = (1.00 L)/300 K) = (V2)/(288 K) ; V2 = 0.960 L YOU MUST USE KELVIN !
7. Choice c can be found by considering Avogadro’s Law, which says that volumes of gases are proportional to # moles at constant P and T. We
can therefore use the mole ratio to solve: (1.00 L O3)*(3 moles O2)/(2 moles O3) = 1.50 L O2
8. Choice a. Use the Ideal Gas Law, PV = nRT, and rearrange: P = nRT/V = (22.0g/(28.0g/mol))*(0.08206 L*atm/mol*K)(25+273K) = 0.961 atm
Note that due to units for R, we must use Kelvin!
20.0 L
9. Choice b correctly predicts the pressure. First of all, we expect the pressure to decrease because the temperature is decreasing and the
volume is being expanded. To solve numerically we use the combined form of the Ideal Gas Law for changing conditions:
P1V1/T1= P2V2 /T2 = (1.80 atm)(50.0 mL) = P2(100.0 mL)
= P2 = 0.567 atm
473 K
298 K
10. Choice c. First determine the reaction: 2H2O  2H2 + O2. We see that the moles produced are in a 2/1 ratio, so according to Avogadro’s
Law and Dalton’s Law, 2/3 of the pressure or 413 torr (2/3 x 620 = 413) is due to hydrogen and 1/3 is due to oxygen (1/3 x 620 = 207 torr).
According to Dalton’s Law, the individual pressures add to the total (413 torr + 207 torr = 620 torr).
11. Choice d. Since most gases approximate ideal behavior under a wide range of conditions, the chemical composition of the gas is usually not
important.
12. Choice d correctly identifies a theory as a model that explains behavior. In this section we learn about kinetic molecular theory, which is a
unifying theory that explains all of the gas laws described in this chapter.
13. Choice d incorrectly labels such collisions as inelastic. If that were true, the gas particles would lose energy to the container walls and
eventually stop moving and settle to the bottom of the container.
14. Choice b is a correct interpretation of kinetic molecular theory,
15. Choice a is arrived at by first balancing the equation. We know that hydrocarbons produce CO2 and H2O as products so we can write:
2C2H2(g) + 5O2(g)  4CO2(g) + 2H2O(g)
Next we realize that because the number of moles of gas is proportional to volumes (Avogadro’s Law), we can use the volume relationship along
with molar ratios:
5.2 L C2H2 * (5 L O2)/(2 L C2H2) = 13 L O2