Name:___________________________
Date:________________
Period:____
Review – Unit 6 Test (Chp 10): Gases
Section I Multiple Choice
NO CALCULATOR
___1. A sample of an ideal gas is heated from 100.0 °C to 150.0 °C in a sealed container of constant
volume. Which of the following values for the gas will increase?
I. The average density of the gas
II. The average number of collisions with the walls of the container
III. The average kinetic energy of the molecules
(A) I only
(B) II only
(C) III only
(D) I and II
(E) II and III
___2.
A sample of 5.0 grams of an ideal gas at 37°C and 2.0 atmosphere pressure has a volume of
3.0 liters. Which of the following expressions is correct for the molar mass of the gas?
(A) (0.08206)(310)
(5.0)(2.0)(3.0)
(B) (5.0)(0.08206)(3.0)
(2.0)(310)
(C) (5.0)(0.08206)(310)
(2.0)(3.0)
(D) (0.08206)(2.0)(3.0)
(5.0)(310)
(E)
(2.0)(3.0)_____
(5.0)(0.08206)(310)
___3.
A flexible metal tank contains nitrogen gas. Which of the following applies to the gas in the tank
when additional nitrogen is added at constant temperature?
(A) The volume of the gas increases.
(B) The pressure of the gas decreases.
(C) The average speed of the gas molecules increases.
(D) The total number of gas molecules remains the same.
(E) The average distance between the gas molecules increases.
___4.
Equal numbers of moles of F2(g), Cl2(g), and Br2(g) are placed in a glass vessel at room
temperature. If the glass vessel is complexly broken in pieces, which of the following will be true
regarding the rates of diffusion throughout the room of the three gases?
(A) RF2 > RCl2 > RBr2
(B) RF2 > RBr2 > RCl2
(C) RCl2 > RBr2 > RF2
(D) RBr2 > RF2 > RCl2
(E) RF2 = RBr2 = RCl2
1
___5.
A sample of 92 grams of sodium metal is added to an excess of sulfuric acid. The volume of
hydrogen gas produced at standard temperature and pressure is _____ liters.
(A) 5.05
(B) 11.2
(C) 22.4
(D) 44.8
(E) 67.2
___6.
A mixture of He and Ne at a total pressure of 0.50 atm is found to contain 1.2 mol of He and
0.80 mol of Ne. The partial pressure of Ne is __________ atm.
(A) 0.20
(B) 0.30
(C) 0.330
(D) 0.40
(E) 0.50
___7.
A hot-air balloon, shown right, rises. Which of the following is the best explanation for this observation?
(A) The pressure on the walls of the balloon increases with increasing temperature.
(B) The difference in temperature between the air inside and
outside the balloon produces convection currents.
(C) The cooler air outside the balloon pushes in on the walls of the balloon.
(D) The rate of diffusion of cooler air is less than that of warmer air.
(E) The air density inside the balloon is less than that of the surrounding air.
___8.
The system shown above is at equilibrium at 28 °C. At this temperature, the vapor pressure of
water is 28 millimeters of mercury. The partial pressure of O2(g) in the system is ____ mmHg.
(A) 28
(B) 56
(C) 133
(D) 161
(E) 189
2
___9.
Under which of the following conditions of temperature and pressure will H2 gas be expected
to behave least like an ideal gas?
(A) 50 K and 0.10 atm
(B) 50 K and 5.0 atm
(C) 500 K and 0.10 atm
(D) 500 K and 50 atm
___10.
The volume of a sample of air in a cylinder with a movable piston is 2.0 L at a pressure P1, as shown
in the diagram above. The volume is increased to 5.0 L as the temperature is held constant. The
pressure of the air in the cylinder is now P2 . What effect do the volume and pressure changes have on
the average kinetic energy of the molecules in the sample?
The average kinetic energy would ____________. (increase / decrease / stay the same)
The pressure would ____________.
(increase / decrease / stay the same)
The density would ____________.
(increase / decrease / stay the same)
The average molecular speed would ___________. (increase / decrease / stay the same)
11.
A 1.0 mole sample of NO2(g) is pressurized at constant temperature.
On the graph, sketch the expected plot of volume versus
pressure as the gas is pressurized (increased pressure).
V
(liters)
P (atm)
A 1.0 mole sample of NO2(g) is heated at constant pressure.
On the graph, sketch the expected plot of volume versus
temperatre as the gas is heated (increased temperature).
V
(liters)
T (K)
A 1.0 mole sample of NO2(g) is heated at constant volume.
On the graph, sketch the expected plot of pressure versus
temperature as the gas is heated (increased temperature).
P
(atm)
T (K)
3
Questions 12-14 refer to the following.
The table below contains information about samples of four different gases at 273 K.
The samples are in four identical rigid containers numbered 1 through 4.
___12.
On the basis of the data provided above, the gas in container 3 could be
(A) CH4
(B) O2
(C) Ar
(D) CO2
___13.
Under the conditions given, consider containers 1, 2, and 4 only.
The average speed of the gas particles is
(A) greatest in container 1
(B) greatest in container 2
(C) greatest in container 4
(D) the same in containers 1, 2, and 4
___14.
The best explanation for the lower pressure in container 4 is that SO2 molecules
(A) have a larger average speed than the other three gases
(B) occupy a larger portion of the container volume than the other three gases
(C) have stronger intermolecular attractions than the other three gases
(D) contain pi bonds, while the other gases contain only sigma bonds
15.
The graph below shows the speed distribution of molecules in a sample of a gas at a certain
temperature. Sketch a graph on the same chart showing the speed distribution of the same molecules at
a higher temperature (as a dashed curve).
4
___16.
Suppose you had 1.0 mol samples of the following gases at STP. If the volume of each sample
of gas was reduced to one tenth of its original size and the temperatures remained the same,
which gas would have the highest pressure?
(A)
(B)
(C)
(D)
(E)
___17.
A chemist puts 1.0 mol of He(g) , 1.0 mol of Ar(g), and 1.0 mol of Xe(g) in to a 1.0 L evacuated
cylinder at STP. The volume of the cylinder is then reduced to one fifteenth of its original size.
Which if the following would be true?
(A)
(B)
(C)
(D)
(E)
___18.
PAr
PHe
PXe
PXe
PHe
<
<
<
<
<
PHe
PAr
PHe
PAr
PXe
<
<
<
<
<
PXe
PXe
PAr
PHe
PAr
A hydrocarbon has a density of about 1.5 g/L at STP. What is the molecular formula of the hydrocarbon?
(A)
(B)
(C)
(D)
(E)
___19.
He
Xe
O3
HCl
CO2
CH2
CH3OH
C4H10
CH3COOH
C3H8
An 11.0 g sample of which gas will have a dry volume of about 5.6 L at STP?
(A)
(B)
(C)
(D)
(E)
O2
Cl2
H2
Kr
CO2
5
Review – Unit 6 Test (Chp 10): Gases
Section II Free Response
Calculator Allowed
CLEARLY SHOW THE METHODS USED AND STEPS INVOLVED IN YOUR ANSWERS. It is to your
advantage to do this, because you may earn partial credit if you do and little or no credit if you do not.
Attention should be paid to significant figures.
1.
0.50 mol
O3(g)
1.0 mol
O2(g)
1.0 L
298 K
1.0 L
298 K
Consider two containers of volume 1.0 L at 298 K, as shown above. One container holds 0.50 mol
O3(g) and the other holds 1.0 mol O2(g). Assume that the O3(g) and the O2(g) exhibit ideal behavior.
(a) Is the pressure in the container holding the O2(g) less than, greater than, or equal to the
pressure in the container holding the O3(g) ? Justify your answer. (2)
(b) The molecules of which gas, O3 or O2, have the greater average speed? Justify your answer.
(1)
(c) What measurement could be made that is directly proportional to the average kinetic energy of
the O3(g) molecules in the container? (1)
(d) If the volume of the container holding the O3(g) was increased to 2.0 L at 298 K, what would
be the change in each of the following variables? In each case, justify your answer.
(i)
The pressure within the container (2)
(ii)
The average speed of the O3(g) molecules (1)
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2.
Use appropriate chemical principles to explain the observation that methane gas behaves as an ideal
gas at low pressure and high temperature. (2)
3.
A valve separates two flasks of gases as follows. A 2.0 L flask contains H2 at a pressure of 5.0 atm,
and a 6.0 L flask contains C3H8 at a pressure of 2.0 atm. Calculate the total pressure of the system
after the valve is opened. Assume the temperature remains constant. (2)
7
4.
Consider the hydrocarbon methane, CH4 (molar mass 16.04 g/mol)
a. Write the balanced equation for the combustion of methane to yield carbon dioxide and water.
(1)
b. What volume of dry carbon dioxide, measured at 20oC and 745 mm Hg, will result from the
complete combustion of 7.00 g of methane? (3)
c. Which gas, CH4 or He , will effuse at twice the rate of the other gas?
Use kinetic-molecular theory to justify your answer. (2)
5.
Lab question.
Study your Lab carefully. Be familiar with the equipment and procedure.
Be especially familiar with the calculations and the error analysis.
-be able to calculate molar mass using
PV = nRT & n = m
M
-know the measurements needed for this experiment
OR
M = mRT
PV
-be able to discuss sources of error for a molar mass too small or too large
use M = mRT
you can discuss if M will be too large or too small due to having a
PV
too small or too large number in the numerator or denominator and
having multiplied or divided by a it.
8