Deck 6: Gases

Question 1

Until recently, materials had to be cooled to temperatures on the order of 4 K to become superconducting. A ceramic has been discovered that becomes superconducting at 92 K. Which of the following temperatures corresponds to 92 K?

A) 32 °F
B) -181°C
C) 212°F
D) 181°C
E) 365 °C

Answer 1

-181°C

Question 2

At what temperature are the readings on the Celsius and Fahrenheit scales the same? At what temperature are the magnitudes the same but the signs different?

Answer 2

-40 °C = -40 °F; -11.4 °C = 11.4 °F

Question 3

What is the melting point of table salt (NaCl) in degrees Fahrenheit, if salt melts at 801°C?

A) 463 °F
B) 477 °F
C) 1441 °F
D) 1474 °F
E) 1499 °F

Answer 3

1474 °F

Question 4

Fahrenheit defined 0° as the lowest temperature that could be achieved by adding salt to ice and found that ice by itself freezes at 32° on this scale. Unfortunately, Fahrenheit's measurements were wrong. The lowest temperature that can be achieved by adding salt to ice is -21.2 °C. Calculate the equivalent temperature on the Fahrenheit scale.

A) -38.2 °F
B) -11.8 °F
C) -6.2 °F
D) 20 °F
E) 32 °F

Question 5

The Kelvin scale is an absolute temperature scale on which one unit, or one Kelvin, is equal to one unit, or one degree, on the Celsius scale. The Rankine scale is an absolute temperature scale on which one unit is equal to one degree on the Fahrenheit scale. Calculate the temperature on the Fahrenheit scale that corresponds to zero on the Rankine scale.

Question 6

Which of the following elements or compounds is most likely to be a gas at room temperature?

A) a metal such as sodium (Na)
B) an alloy of two metals such as bronze, which is a mixture of copper (Cu) and tin (Sn)
C) a salt such as MgO
D) a nonmetal such as chlorine (Cl₂)
E) none of these elements or compounds will be a gas at room temperature

Question 7

Which of the following relationships between the two variables listed for an ideal gas does $\textbf{ not }$ give a straight line graph with a positive slope?

A) P and T
B) n and V
C) P and V
D) T and V
E) none of these

Question 8

How many cm³ of liquid SO₂ (d = 1.46 g/cm³) can be obtained by compressing 1.00 liter of the gas collected at 25°C and 1 atm?

Question 9

Three containers of equal volume are filled with three different gases. The first container is filled with Ar, the second with O2 and the third with CO2. The pressure and temperature of the three gases are the same. Which of the following is true of the gases in the three containers?

A) The number of moles of gas in the containers is the same.
B) The masses of gas in the three containers are the same.
C) The density of gas in the three containers is the same.
D) (a), (b), and (c) are all true.
E) None of these are true.

Question 10

Samples of oxygen and helium have been collected in two separate containers of equal volume. Both gases have the same temperature and pressure. Which of the following statements is true?

A) The container of oxygen has the larger number of moles of gas.
B) The container of helium has the larger mass of gas.
C) The container of helium has the larger number of moles of gas.
D) Both containers have the same mass of gas.
E) Both containers have the same number of moles of gas.

Question 11

The density of neon gas will be greatest at:

A) 0 C and 1 atm
B) 273 11ee9eac_9a2c_e10d_9fac_318e34c8dfe1_TB9692_11 C and 1.5 atm
C) 0 11ee9eac_9a2c_e10d_9fac_318e34c8dfe1_TB9692_11 C and 2 atm
D) 273 11ee9eac_9a2c_e10d_9fac_318e34c8dfe1_TB9692_11 C and 1 atm
E) The density of neon will be the same for all of the above cases.

Question 12

Calculate the volume in liters occupied by 2.0 g of Ne at 50.0 C and 1.5 atm of pressure.

A) 1.1 L
B) 8.8 L
C) 35 L
D) 47 L
E) none of these

Question 13

Ether was one of the first anesthetics discovered. Assume that several mL of ether are placed in a bulb with a volume of 293 mL, and the bulb is immersed in water at 36°C until the last drop of liquid disappears, leaving the bulb filled with ether vapor. The bulb is then removed from the water bath, and the weight of ether that condenses in the bulb is measured. If 0.841 grams of ether collect in this experiment at a pressure of 746 mmHg, what is the molecular weight of ether?

Question 14

Which sample would have the largest volume at 25°C and 750 mmHg?

A) 25 g NH₃
B) 25 g C₂H₂
C) 25 g NO₂
D) 25 g Ar
E) All of these samples would have the same volume at 25°C and 750 mmHg.

Question 15

What is the volume, in liters, of 1.00 mole of an ideal gas at 25.0°C and 1.00 atm pressure?

A) 0.0409 L
B) 2.05 L
C) 22.4 L
D) 24.5 L
E) none of the above

Question 16

A small gas cylinder of helium used in chemistry lecture demonstrations has a volume of 275 mL at a pressure of 1823 kPa at 24.7°C. Use this information to answer

-The volume of helium, in mL, needed to fill the cylinder at 772 torr and 24.7°C is:

A) 45.9 mL
B) 303 mL
C) 4.87 x 10³ mL
D) 4.95 x 10⁴ mL
E) 4.86 x 10⁵ mL

Question 17

A small gas cylinder of helium used in chemistry lecture demonstrations has a volume of 275 mL at a pressure of 1823 kPa at 24.7°C. Use this information to answer

-At what temperature in degrees Celsius would the helium gas in the cylinder exhibit a pressure of 25.0 atm?

A) 4.96°C
B) 34.3°C
C) 58.8°C
D) 140°C
E) 307°C

Question 18

A small gas cylinder of helium used in chemistry lecture demonstrations has a volume of 275 mL at a pressure of 1823 kPa at 24.7°C. Use this information to answer

-The number of grams of helium in the cylinder is:

A) 0.202 g
B) 0.810 g
C) 1.24 g
D) 4.96 g
E) none of these

Question 19

Polypropylene is a plastic formed by polymerizing propylene, which has the empirical formula CH₂. If a sample of propylene with a mass of 21.0 grams occupies a volume of 11.2 L at STP (0 °C and 1 atm), what is the molecular formula of this gas?

A) CH₂
B) C₂H₄
C) C₃H₆
D) C₄H₈
E) none of these

Question 20

A 2.91 gram sample of a gaseous compound that contains only boron and hydrogen has a volume of 1.22 L at 25°C and 1.09 atm. What is the formula of this compound?

A) B₂H₆
B) B₄H₁₀
C) B₅H₉
D) B₆H₁₀
E) B₆H₁₂

Question 21

What volume of NH₃(g) at STP is required to prepare 49.8 g of (NH₄)₂SO₄ by the reaction of ammonia with sulfuric acid?

A) 0.377 L
B) 6.41 L
C) 8.4 L
D) 12.84 L
E) 16.9 L

Question 22

Uranium reacts with fluorine to produce a compound that is a gas at 57°C. The density of this gas is 13.0 g/L at 57°C and 1 atm pressure. What is the molecular formula of this compound?

A) UF₂
B) UF₃
C) UF₄
D) UF₅
E) UF₆

Question 23

Which of the following gases would have the largest density at 25°C and 1.00 atm pressure?

A) methane, CH₄
B) acetylene, C₂H₂
C) ethylene, C₂H₄
D) ethane, C₂H₆
E) propane, C₃H₈

Question 24

Which of the following gases has a density of 1.72 g/L at 10°C and 1 atm pressure?

A) He
B) Ne
C) Ar
D) CH₄
E) P₄

Question 25

What is the density of NO(g) at 25.0°C and 783 mmHg?

A) 1.26 g/L
B) 2.68 g/L
C) 3.12 g/L
D) 3.76 g/L
E) 22.4 g/L

Question 26

Nitrogen gas reacts with hydrogen gas to produce gaseous ammonia (NH₃). How many liters of product at STP can be formed if 6 L of hydrogen gas at STP reacts with a stoichiometric amount of nitrogen gas?

A) 1 L
B) 2 L
C) 3 L
D) 4 L
E) 6 L

Question 27

We want to increase the volume of a fixed amount of gas from 68.2 to 153 mL while holding the pressure constant. To what temperature in degrees Celsius must we heat this gas if the initial temperature is 21.0 °C?

A) 47.1 °C
B) 387 °C
C) 660 °C
D) 89.5 °C
E) not enough information given

Question 28

0.500 mol of Ar gas occupies a volume of 4.07 L at 25.0 °C and 3.00 atm pressure. What volume will the gas occupy at STP (0.00°C and 1.00 atm pressure)?

A) 1.24 L
B) 1.48 L
C) 4.07 L
D) 11.2 L
E) 13.3 L

Question 29

A cylindrical container with a movable piston initially holds 1.5 moles of gas
At a pressure of 4.0 atmospheres and a volume of 2.5 liters. If the piston is moved to create a volume of 5.0 liters while simultaneously withdrawing 0.75 moles of gas, what is the final pressure if the temperature is constant?

A) 0.50 atm
B) 1.0 atm
C) 2.0 atm
D) 4.0 atm
E) 8.0 atm

Question 30

What is the final temperature in kelvins if a sample of ammonia gas, initially at a pressure of 3.00 atmospheres, a temperature of 500.0 K, and a volume of 275 L is changed to a volume of 200.0 L and a pressure of 2.50 atm?

A) 303 K
B) 436 K
C) 573 K
D) 825 K
E) none of the above

Question 31

At 25°C and one atmosphere pressure, four fifths of the pressure of the atmosphere is due to N₂ and one fifth is due to O₂. What fraction of the pressure at 10 atm. and 100°C would be due to N₂?

Question 32

A gas cylinder contains the following mixture of gases: 10 g H₂, 15 g CH₄, 20 g SO₂ and 12 g Ar. Which gas exerts the largest partial pressure in the container?

A) H₂
B) CH₄
C) SO₂
D) Ar
E) all exert the same pressure

Question 33

A sealed 2.00 L container at 20.0^oC holds 150.0 g of ammonia (NH₃), 150.0 g of carbon dioxide (CO₂), and 150.0 g of nitrogen(N₂). What is the total pressure in atmospheres?

A) 155
B) 0. 0227
C) 211 atm.
D) 0. 333
E) The pressure can't be determined from the information given.

Question 34

What is the total pressure in atmospheres when 0.400 g of H₂, 2.00 g of N₂, and 10.5 g of CO₂ are injected into a 10.0 liter flask at 273 K?

A) 0.571 atm
B) 0.877 atm
C) 1.14 atm
D) 1.75 atm
E) it is impossible to determine the answer from the data given

Question 35

0.300 L of H₂ gas was collected over water at 27.0°C on a day when the atmospheric pressure was 745 torr. What would be the volume of H₂ gas at 760 torr after the water vapor was removed? (P_H2O = 27.0 torr at 27°C)

A) 0.283 L
B) 0.294 L
C) 0.300 L
D) 0.306 L
E) 0.318 L

Question 36

Calculate the volume of the flask that would contain 0.40 moles of oxygen, 0.600 moles of nitrogen, and 1.50 moles of hydrogen at 25.0°C and a total pressure of 1.80 atm. Calculate the partial pressure of each gas.

Question 37

Oxygen is bubbled through water before it is given to a patient in a hospital.
What volume of pure oxygen gas at 21.0°C and 750.0 torr pressure would a patient receive if the patient breathed 0.250 L of O₂ bubbled through water at this temperature and pressure? (P_H2O = 19.0 torr at 21°C)

A) 0.00633 L
B) 0.244 L
C) 0.250 L
D) 0.256L
E) none of the above

Question 38

Use the Kinetic Molecular Theory to explain on the molecular level the following observations for an ideal gas.
I) Decreasing the volume causes an increase in pressure if temperature and number of moles are held constant.
II) Increasing the temperature causes an increase in pressure if volume and number of moles are held constant.

Question 39

Use the Kinetic Molecular Theory of gases to explain why pressure of a gas is proportional to its temperature in a fixed volume container.

Question 40

Which of the following can explain the increase in pressure that results from decreasing the volume of a fixed amount of gas at a fixed temperature?

A) The gas molecules move faster and therefore hit the walls of the container with more force.
B) The gas molecules have a shorter path between the walls of the container and therefore collide with the walls more frequently.
C) The gas molecules increase in their apparent mass therefore exerting more force when they strike the walls of the container.
D) The gas molecules collide less with each other therefore having more force to exert on the walls of the container.
E) None of these.

Question 41

Why does a hot air balloon rise when the air in the balloon is heated?

A) The average kinetic energy of the air molecules increases, and the collisions between these molecules and the walls of the balloon make it rise.
B) The pressure of the gas inside the balloon increases, pushing up on the balloon.
C) The gas expands, forcing some of the gas to escape from the bottom of the balloon, and the decrease in the density of the gas lifts the balloon.
D) The balloon expands, causing it to rise.
E) The hot air rises inside the balloon, which produces enough force to lift the balloon.

Question 42

Which would always lead to an increase in the average kinetic energy of a gas?

A) Increasing the volume by decreasing the pressure.
B) Increasing the pressure by decreasing the volume.
C) Increasing the pressure by increasing the number of molecules of gas.
D) Increasing the volume by increasing the temperature of the gas.
E) All of the above are equally effective ways of increasing the average kinetic energy of a gas.

Question 43

Which isn't a basic assumption of the kinetic theory?

A) Gases consist of a large number of tiny particles in constant random motion.
B) The distance between gas particles is large compared with their diameters, and therefore most of the volume of a gas is empty space.
C) Gas particles move in a straight line until they collide with another gas particle or the walls of the container.
D) The average kinetic energy of the particles in a gas is proportional only to the temperature of the gas.
E) All of the above are basic assumptions of the kinetic theory.

Question 44

Which isn't one of the postulates of the kinetic molecular theory?

A) At a constant temperature, all of the particles have the same speed.
B) Gas particles are in constant motion.
C) Gas particles move in a straight line between collisions.
D) The volume of the particles is negligibly small compared to the volume of the container.
E) There are no forces of attraction between gas particles.

Question 45

Which isn't a postulate of the kinetic molecular theory?

A) The mass of a molecule is negligibly small.
B) The volume of a molecule is a negligibly small fraction of the volume of the container.
C) The number of molecules in a gas is very large.
D) The molecules are in a state of constant, random motion.
E) The attractive forces between molecules are negligibly small.

Question 46

If the average speed of O₂ molecules at STP is 4.3 x 10² meters per second, what is the average speed of H₂ molecules at the same temperature and pressure?

A) 1.1 x 10²
B) 2.2 x 10²
C) 8.6 x 10²
D) 1.7 x 10³
E) none of the above

Question 47

The root-mean-square speed of CH₄ molecules at 25°C is about 0.56 km/s. What is the root-mean-square speed of a H₂ molecule at 25°C?

A) 0.070 km/s
B) 0.20 km/s
C) 1.1 km/s
D) 1.6 km/s
E) 4.5 km/s

Question 48

Assume that a container is filled with a mixture of SO₃ and Ne. The molecular weight of SO₃ is 80 g/mol and the atomic weight of Ne is 20 g/mol. The average velocity of an SO₃ molecule is:

A) one-fourth that of a Ne atom.
B) one-half that of a Ne atom.
C) the same as a Ne atom.
D) two times that of a Ne atom.
E) 4 times that of a Ne atom.

Question 49

Which of the following gases would diffuse fastest at room temperature?

A) NH₃
B) CO
C) H₂S
D) F₂
E) CO₂

Question 50

Nitrogen and oxygen are allowed to effuse through a porous barrier at 295 K. If nitrogen effuses at a rate of 0.0355 moles per minute, what is the rate of effusion of oxygen?

A) 0.0311 mol/min
B) 0.0332 mol/min
C) 0.0380 mol/min
D) 0.0405 mol/min
E) 31.1 mol/min

Question 51

²³⁵U (234.040947 amu) and ²³⁸U (235.043925 amu) are separated on the basis of the relative rates of diffusion of ²³⁵UF₆ and ²³⁸UF₆. Calculate the relative rates of diffusion of these two compounds.

Question 52

The ideal gas equation predicts that a plot of the pressure times the volume of a gas versus the pressure of this gas should be a horizontal straight line at a fixed temperature. When these quantities are graphed for CO₂, however, we find that PV dips far below the theoretical straight line at first. This can be explained as follows.

A) The force of attraction between the CO₂ molecules makes the product of the pressure times the volume of this gas smaller than predicted from the ideal gas equation.
B) The volume of the CO₂ molecules makes the product of the pressure times the volume of this gas smaller than predicted from the ideal gas equation.
C) The force of attraction between the CO₂ molecules makes the product of the pressure times the volume of this gas larger than predicted from the ideal gas equation.
D) The volume of the CO₂ molecules makes the product of the pressure times the volume of this gas larger than predicted from the ideal gas equation.
E) There is no way to explain the difference between a real gas and the predictions of the ideal gas equation.

Question 53

Calculate the volume of hydrogen bromide that can be prepared by reacting 10.0 grams of phosphorus tribromide with excess water at 21°C and 753 mmHg.
PBr₃(l) + 3 H₂O(l) $\rightarrow$ 3 HBr(g) + H₃PO₃(aq)

Question 54

Calculate the volume of oxygen at 0°C and 1 atm pressure that can be produced by decomposing 100 mL of hydrogen peroxide if this solution is 27.6% H₂O₂ by weight and the density is 1.09 g/cm³.
2 H₂O₂(l) $\rightarrow$ 2 H₂O(l) + O₂(g)

Question 55

2.11 moles of C₃H₈ are allowed to burn in the presence of excess O₂ to form CO₂ and H₂O.

C₃H₈(g) + 5 O₂(g) $\rightarrow$ 3 CO₂(g) + 4 H₂O(g)
The carbon dioxide is isolated from all other gases and stored in a 1.25 L container at 0.00°C. What is the pressure in this container if the gas obeys the ideal gas equation?

A) 18 atm
B) 38 atm
C) 113 atm
D) 1,130 atm
E) none of the above

Question 56

What is the empirical formula of the only product of the following reaction

__ N₂O₃(g) + __ O₃(g) $\rightarrow$
If 3.00 L of N₂O₃ react completely with 1.00 L of O₃ to give 6.00 L of the product, all gases measured at STP?

A) NO
B) NO₂
C) NO₃
D) N₂O₅
E) none of the above

Question 57

Two identical flasks are at the same temperature. One is filled with 2 grams of hydrogen, the other with 28 grams of nitrogen gas. Which property would be significantly different for the two samples?

A) pressure
B) average kinetic energy
C) density
D) the number of molecules in each container
E) the number of moles of gas in each container

Question 58

Cyclopropane, a gas containing only carbon and hydrogen, is an anesthetic.
If 0.450 L of cyclopropane at 120°C and 0.720 atm reacts with excess O₂ to give 1.35 L of CO₂(g) and 1.35 L of H₂O(g) at the same temperature and pressure, what is the percent by weight of carbon in cyclopropane?

A) 33.3%
B) 41.8%
C) 45.0%
D) 85.7%
E) 90.0%

Question 59

A metal reacts with acid to form hydrogen gas as shown by the following equation.

M(s) + 2 H⁺(aq) $\rightarrow$ M²⁺(aq) + H₂(g)
What is the atomic weight of this metal if 3.49 grams of the metal generates enough hydrogen collected over water to fill a bottle with a volume of 2.20 L at 25.0°C and 1.00 atmosphere pressure under conditions where the vapor pressure of the solution is 23.8 torr?

A) 19.4 g/mol
B) 37.6 g/mol
C) 38.8 g/mol
D) 40.0 g/mol
E) none of the above