Gas Law MC Practice Test
The graph above shows the distribution of molecular speeds for four different gases at the same temperature. What property of the different gases can be correctly ranked using information from the graph, and why?
The molecular masses of the gases, because the gas molecules have the same average kinetic energy and mass can be calculated using the equation KEavg=12mv2KEavg=12mv2.
A 2 L sample of N2(g) and a 1 L sample of Ar(g), each originally at 1 atm and 0°C, are combined in a 1 L tank. If the temperature is held constant, what is the total pressure of the gases in the tank?
3 atm
The following questions refer to the 1 L flasks shown below. Which flask contains the sample with the greatest density?
C 40 degrees 2 atm
A 2 L container will hold about 4 g of which of the following gases at 0°C and 1 atm?
CO2
The diagram above shows the distribution of speeds for a sample of N2(g) at 25°C. Which of the following graphs shows the distribution of speeds for a sample of O2(g) at 25°C (dashed line) ?
high relative molecules low speed
Given that the density of Hg(l) at 0°C is about 14 g mL-1, which of the following is closest to the volume of one mole of Hg(l) at this temperature?
14 mL
A flask contains 0.25 mole of SO2(g), 0.50 mole of CH4(g), and 0.50 mole of O2(g). The total pressure of the gases in the flask is 800 mm Hg. What is the partial pressure of the SO2(g) in the flask?
160 mm Hg
When 6.0 L of He(g) and 10. L of N2(g), both at 0oC and 1.0 atm, are pumped into an evacuated 4.0 L rigid container, the final pressure in the container at 0oC is
4.0 atm
The figure above represents three sealed 1.0 L vessels, each containing a different inert gas at 298 K. The pressure of Ar in the first vessel is 2.0 atm. The ratio of the numbers of Ar, Ne, and He atoms in the vessels is 2:1:6, respectively. After all the gases are combined in a previously evacuated 2.0 L vessel, what is the total pressure of the gases at 298 K?
4.5 atm
Which of the following best helps explain why the pressure of a sample of CH4(g) (molar mass 16g/mol) is closer to the pressure predicted by the ideal gas law than a sample of NH3(g) (molar mass 17g/mol) ?
NH3NH3 molecules are polar while CH4CH4 molecules are not, and the greater attractions between NH3NH3 molecules cause the molecules to collide with the walls of the container with less force.
Equal numbers of moles of He(g), Ar(g), and Ne(g) are placed in a glass vessel at room temperature. If the vessel has a pinhole-sized leak, which of the following will be true regarding the relative values of the partial pressures of the gases remaining in the vessel after some of the gas mixture has effused?
PHe < PNe < PAr
A 1L sample of helium gas at 25°C and 1atm is combined with a 1L sample of neon gas at 25°C and 1atm. The temperature is kept constant. Which of the following statements about combining the gases is correct?
The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.
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 stays the same.
A rigid metal tank contains oxygen gas. Which of the following applies to the gas in the tank when additional oxygen is added at constant temperature?
The average speed of the gas molecules remains the same.
A vessel contains Ar(g) at a high pressure. Which of the following statements best helps to explain why the measured pressure is significantly greater than the pressure calculated using the ideal gas law?
The combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container.
The diagrams above represent two samples of Xe gas in containers of equal volume at 280K. Which of the following correctly compares the two samples in terms of their deviation from ideal gas behavior and explains why?
The gas in sample 2 would deviate more from ideal behavior because the XeXe atoms are closer together, leading to an increase in intermolecular attractions.
Refer to three gases in identical rigid containers under the conditions given in the table below. The density of the gas, in g/L, is
greatest in container B
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. The best explanation for the lower pressure in container 4 is that SO2 molecules
have stronger intermolecular attractions than the other three gases
The distribution of speeds of H2(g) molecules at 273 K and 1 atm is shown in the diagram above. Which of the following best shows the speed distribution of He(g) atoms under the same conditions of temperature and pressure?
high fraction of partictles low speed
Questions refer to three gases in identical rigid containers under the conditions given in the table below. The average kinetic energy of the gas molecules is
the same in all three containers
When the actual gas volume is greater than the volume predicted by the ideal gas law, the explanation lies in the fact that the ideal gas law does NOT include a factor for molecular.
volume
Which of the following gases deviates most from ideal behavior?
SO2
The following questions refer to the 1 L flasks shown below. In which flask do the molecules have the greatest average speed?
B 50 degrees .5 atm
Refer to three gases in identical rigid containers under the conditions given in the table below. The average kinetic energy of the gas molecules is
D the same in all three containers
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. Under the conditions given, consider containers 1, 2, and 4 only. The average speed of the gas particles is
greatest in container 1
A sample of an unknown gas from a cylinder is collected over water in the apparatus shown above. After all the gas sample has been collected, the water levels inside and outside the gas collection tube are made the same. Measurements that must be made to calculate the molar mass of the gas include all of the following EXCEPT
mass of the water in the apparatus
The pressure, in atm, exerted by 1.85 mol of an ideal gas placed in a 3.00 L container at 35.0°C is given by which of the following expressions?
(1.85)(0.0821)(308)/3.00 atm
A sealed vessel contains 0.200 mol of oxygen gas, 0.100 mol of nitrogen gas, and 0.200 mol of argon gas. The total pressure of the gas mixture is 5.00 atm. The partial pressure of the argon is
2.00 atm
At standard temperature and pressure, a 0.50 mol sample of H2 gas and a separate 1.0 mol sample of O2 gas have the same
average molecular kinetic energy
An equimolar mixture of N2(g) and Ar(g) is kept inside a rigid container at a constant temperature of 300 K. The initial partial pressure of Ar in the mixture is 0.75atm. An additional amount of Ar was added to the container, enough to double the number of moles of Ar gas in the mixture. Assuming ideal behavior, what is the final pressure of the gas mixture after the addition of the Ar gas?
2.25atm, because doubling the number of moles of ArAr doubles its partial pressure.
Equal masses of He and Ne are placed in a sealed container. What is the partial pressure of He if the total pressure in the container is 6 atm?
5 atm
A gas mixture at 0°C and 1.0atm contains 0.010mol of H2, 0.015mol of O2, and 0.025mol of N2. Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture?
About 0.20atm0.20atm, because H2H2 comprises 20%20% of the total number of moles of gas.
PCl5(g) ⇄ PCl3(g)+Cl2(g) PCl5(g) decomposes into PCl3(g) and Cl2(g) according to the equation above. A pure sample of PCl5(g) is placed in a rigid, evacuated 1.00L container. The initial pressure of the PCl5(g) is 1.00 atm. The temperature is held constant until the PCl5(g) reaches equilibrium with its decomposition products. The figures below show the initial and equilibrium conditions of the system. Which of the following is the most likely cause for the increase in pressure observed in the container as the reaction reaches equilibrium?
An increase in the number of molecules, which increases the frequency of collisions with the walls of the container
Refer to the following. PCl5(g) ⇄ PCl3(g) + Cl2(g) PCl5(g) decomposes into PCl3(g) and Cl2(g) according to the equation above. A pure sample of PCl5(g) is placed in a rigid, evacuated 1.00 L container. The initial pressure of the PCl5(g) is 1.00 atm. The temperature is held constant until the PCl5(g) reaches equilibrium with its decomposition products. The figures below show the initial and equilibrium conditions of the system. Which of the following is the most likely cause for the increase in pressure observed in the container as the reaction reaches equilibrium?
An increase in the number of molecules, which increases the frequency of collisions with the walls of the container
The following questions refer to the 1 L flasks shown below. Which flask contains the smallest number of moles of gas?
B N2
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. On the basis of the data provided above, the gas in container 3 could be
CH4
Which of the following behaves most like an ideal gas at the conditions indicated?
H2(g) molecules at 10-3 atm and 200oC
The experimental apparatus represented above is used to demonstrate the rates at which gases diffuse. When the cotton balls are placed in the ends of a tube at the same time, the gases diffuse from each end and meet somewhere in between, where they react to form a white solid. Which of the following combinations will produce a solid closest to the center of the tube?
HCl and CH3NH2 This option is correct. It demonstrates understanding that gases with similar molar masses (HCl = 36 g/mol and CH3NH2 = 31 g/mol) at the same temperature will travel with similar average speeds, resulting in a solid being formed at roughly equal distances from each cotton ball.
A 0.5 mol sample of He(g) and a 0.5 mol sample of Ne(g) are placed separately in two 10.0 L rigid containers at 25°C. Each container has a pinhole opening. Which of the gases, He(g) or Ne(g), will escape faster through the pinhole and why?
He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.
A sample of an ideal gas is cooled from 50.0C to 25.0C in a sealed container of constant volume. Which of the following values for the gas will decrease? I. The average molecular mass of the gas II. The average distance between the molecules III. The average speed of the molecules
III only
Equal masses of three different ideal gases, X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements about the partial pressure of gas X is correct?
It depends on the relative molecular masses of X, Y, and Z.
Under which of the following conditions of temperature and pressure would 1.0 mol of the real gas CO2(g) behave most like an ideal gas?
Temperature(K)Pressure(atm)8000.1
Two flexible containers for gases are at the same temperature and pressure. One holds 0.50 gram of hydrogen and the other holds 8.0 grams of oxygen. Which of the following statements regarding these gas samples is FALSE?
The average speed of the hydrogen molecules is the same as the average speed of the oxygen molecules.
Diagram 1 above shows equimolar samples of two gases inside a container fitted with a removable barrier placed so that each gas occupies the same volume. The barrier is carefully removed as the temperature is held constant. Diagram 2 above shows the gases soon after the barrier is removed. Which statement describes the changes to the initial pressure of each gas and the final partial pressure of each gas in the mixture and also indicates the final total pressure?
The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases.
Ar(g) deviates more from ideal behavior at extremely high pressures than Ne(g) does. Which of the following is one reason for this difference?
The particle volume of ArAr is greater than that of NeNe.
When a sample of oxygen gas in a closed container of constant volume is heated until its absolute temperature is doubled, which of the following is also doubled?
The pressure of the gas
The reaction between NO(g) and O2(g) to produce NO2(g) in a rigid reaction vessel is represented in the diagram above. The pressure inside the container is recorded using a pressure gauge. Which of the following statements correctly predicts the change in pressure as the reaction goes to completion at constant temperature, and provides the correct explanation?
The pressure will decrease because there are fewer molecules of product than of reactants.
The graph above shows the speed distribution of molecules in a sample of a gas at a certain temperature. Which of the following graphs shows the speed distribution of the same molecules at a lower temperature (as a dashed curve) ?
This option is correct. A decrease in temperature results in a decrease in the average speed of the molecules, as shown here.
Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas
are relatively far apart
At constant temperature, the behavior of a sample of a real gas more closely approximates that of an ideal gas as its volume is increased because the
average distance between molecules becomes greater
Questions refer to three gases in identical rigid containers under the conditions given in the table below. The density of the gas, in g/L, is
greatest in container B