Deck 5: Gases

Question 1

The volume of a helium balloon is 1.85 L at 24.0°C and 1.00 atm at sea level. The balloon is released and floats upward. At a certain altitude, the balloon has a volume of 2.14 L and the temperature is 15.2°C. What is the atmospheric pressure at this altitude?

A) 0.538 atm
B) 1.36 atm
C) 0.839 atm
D) 0.891 atm
E) none of these

Answer 1

0.839 atm

Question 2

Air is 79% N₂ and 21% O₂ by volume. Calculate the density of air at 1.0 atm, 25°C.

A) 1.18 g/L
B) 2.46 g/L
C) 0.590 g/L
D) 14.1 g/L
E) none of these

Answer 2

1.18 g/L

Question 3

Consider three 1-L flasks at the same temperature and pressure. Flask A contains CO gas, flask B contains N₂ gas, and flask C contains O₂ gas.Which contains the lowest density?

A) flask A
B) flask B
C) flask C
D) All are the same.
E) Two of the flasks contain gases at the same density.

Answer 3

Two of the flasks contain gases at the same density.

Question 4

Consider a sample of neon gas in a container fitted with a movable piston (assume the piston is massless and frictionless). The temperature of the gas is increased from 20.0°C to 40.0°C. The density of neon

A) decreases less than 10%.
B) decreases more than 10%.
C) does not change.
D) increases more than 10%.
E) increases less than 10%.

Question 5

A balloon contains 10.0 g of neon gas. With the temperature kept constant, 10.0 g of argon gas is added. What happens?

A) The volume of the balloon expands by more than 2 times.
B) The volume of the balloon expands by less than 2 times.
C) The balloon stays the same size, but the pressure increases.
D) The balloon doubles in volume.
E) none of these

Question 6

Which of the following relationships is not true?

A) PV = constant when temperature and moles of gas are held constant.
B) V/T = constant when pressure and moles of gas are held constant.
C) nT = constant when pressure and volume are held constant.
D) P/n = constant when volume and temperature are held constant.
E) All of these are true.

Question 7

A sample of oxygen gas has a volume of 4.50 L at 27°C and 800.0 torr. How many oxygen molecules does it contain?

A) 1.16 × 10²²
B) 1.16 × 10²³
C) 2.32 × 10²⁴
D) 5.8 × 10²²
E) none of these

Question 8

A cylinder is fitted with a movable piston. The pressure inside the cylinder is P_i and the volume is V_i. What is the new pressure in the system when the piston decreases the volume of the cylinder by half?

A) 2V_iP_i
B) 2P_i
C) (1/4)P_i
D) (1/2)P_i
E) P_i²

Question 9

Mercury vapor contains Hg atoms. What is the volume of 200. g of mercury vapor at a temperature of 822 K and 0.500 atm?

A) 135 L
B) 329 L
C) 82.2 L
D) 67.2 L
E) none of these

Question 10

Samples of the gases H₂(g) and SO₂(g) have equal masses and are at the same temperature and pressure. Calculate the following:
The ratio of volumes

A) 32
B) 0.18
C) 180
D) 5.6
E) 1.0

Question 11

Body temperature is about 308 K. On a cold day, what volume of air at 273 K must a person with a lung capacity of 2.00 L breathe in to fill the lungs?

A) 1.13 L
B) 2.26 L
C) 1.77 L
D) 3.54 L
E) none of these

Question 12

Three 1.00-L flasks at 25°C and 725 torr contain the gases CH₄ (flask A), CO₂ (flask B), and C₂H₆ (flask C).In which flask is there 0.039 mol of gas?

A) flask A
B) flask B
C) flask C
D) all
E) none

Question 13

Given a cylinder of fixed volume filled with 1 mol of argon gas, which of the following is correct? (Assume all gases obey the ideal gas law.)

A) If a second mole of argon is added to the cylinder, the ratio T/P will remain constant.
B) If the temperature of the cylinder is changed from 25°C to 50°C, the pressure inside the cylinder will double.
C) A cylinder of identical volume filled with the same pressure of helium must contain more atoms of gas because He has a smaller atomic radius than argon.
D) Two of these are correct.
E) None of these is correct.

Question 14

Consider two samples of helium in separate containers of the same volume. Sample 1 has an absolute temperature four times that of Sample 2. Both samples are at the same pressure.Calculate the ratio n₁/n₂.

A) 2:1
B) 1:1
C) 1:2
D) 4:1
E) 1:4

Question 15

The valve between a 3.00-L tank containing O₂(g) at 7.36 atm and a 2.10-L tank containing Ne(g) at 5.08 atm is opened. Calculate the ratio of partial pressures (O₂:Ne) in the container.

A) 0.592
B) 1.45
C) ​1.43
D) ​2.07
E) ​0.483

Question 16

A glass column is filled with mercury and inverted in a pool of mercury. The mercury column stabilizes at a height of 735 mm above the pool of mercury. What is the pressure of the atmosphere?

A) 1.03 atm
B) 194 atm
C) 0.697 atm
D) 0.967 atm
E) 0.735 atm

Question 17

A 8.80-g piece of solid CO₂ (dry ice) is allowed to sublime in a balloon. The final volume of the balloon is 1.30 L at 290. K. What is the pressure of the gas?

A) 7.36 × 10^-5 atm
B) 0.273 atm
C) 3.66 atm
D) 1.61 × 10² atm
E) 44.6 atm

Question 18

A sample of nitrogen gas has a volume of 180.0 mL at STP. What volume does the gas occupy if the absolute temperature and pressure are each doubled?

A) 90.00 mL
B) 360.0 mL
C) 720.0 mL
D) 44.8 L
E) 180.0 mL

Question 19

The volume of a balloon is 3.02 L at 22.7°C. The balloon is heated to 43.6°C. Calculate the new volume of the balloon.

A) 1.57 L
B) 3.02 L
C) 2.82 L
D) 3.23 L
E) 5.80 L

Question 20

A cylinder of oxygen gas contains 26.4 g of O₂. Another cylinder, twice the volume of the cylinder containing oxygen (and at the same conditions of pressure and temperature), contains CO₂ gas. Assuming ideal behavior, what is the mass of the carbon dioxide?

A) 13.2 g
B) 72.6 g
C) 36.3 g
D) 52.8 g
E) none of these

Question 21

The density of a certain diatomic gas is 1.696 g/L at STP. Identify the gas.

A) Cl₂
B) O₂
C) F₂
D) H₂
E) N₂

Question 22

Magnesium metal reacts with hydrochloric acid to form aqueous magnesium chloride and hydrogen gas. An excess of magnesium is reacted with 20.0 mL of 3.00 M hydrochloric acid, and all of the hydrogen is collected in a balloon at 25°C and 1.00 atm. What is the expected volume of the balloon?

A) 0.734 L
B) 1.47 L
C) 0.672 L
D) 22.4 L
E) 1.34 L

Question 23

Equimolar amounts of the gases N₂ and H₂ are mixed in a closed container fitted with a piston (allowing the volume of the container to change, thus keeping the pressure constant). Calculate the ratio of the final volume of the container to the initial volume of the container when the reaction N₂ + 3H₂ → 2NH₃ goes to completion.

A) 1
B) 2/3
C) 3/2
D) 1/3
E) none of these

Question 24

Four identical 1.0-L flasks contain the gases He, Cl₂, CH₄, and NH₃, each at 0°C and
1 atm pressure.
Which gas has the highest density?

A) NH₃
B) CH₄
C) Cl₂
D) He
E) All the gases have the same density.

Question 25

Into a 3.50-liter container at 25°C are placed 1.10 mol of O₂ gas and 4.68 mol of solid C (graphite). If the carbon and oxygen react completely to form CO(g), what will be the final pressure in the container at 25°C?

A) 0.645 atm
B) 7.69 atm
C) 32.7 atm
D) 40.4 atm
E) 15.4 atm

Question 26

Air has an average molar mass of 29.0 g/mol. The density of air at 1.00 atm and 30°C is

A) 40.0 g/mL.
B) 1.17 g/L.
C) 1.29 g/L.
D) 12 g/L.
E) 29.0 g/L.

Question 27

A volatile liquid produced 0.379 g of vapor in a 262.0-mL flask at 100.0°C and 0.960 atm. What is the molar mass of the liquid?

A) 11.9 g/mol
B) 35.4 g/mol
C) 46.1 g/mol
D) 8.22 g/mol
E) 30.7 g/mol

Question 28

An excess of potassium hydroxide is treated with 1.6 L of dry hydrogen bromide gas measured at STP. What is the mass of potassium bromide formed?

A) 8.2 × 10² g
B) 8.5 g
C) 1.0 × 10³ g
D) 1.7 × 10³ g
E) 1.4 × 10³ g

Question 29

At STP the mass of 680.0 mL of a certain gas is 0.850

A) CO
B) Ar
C) O₂
D) CO₂
E) H₂

Question 30

What volume of carbon dioxide measured at STP will be formed by the reaction of 1.30 mol of oxygen with 9.00 × 10^-1 mol of ethyl alcohol (CH₃CH₂OH)?

A) 91.9 L
B) 8.70 L
C) 28.0 L
D) 19.4 L
E) 40.3 L

Question 31

Air is 79% N₂ and 21% O₂ by volume. Calculate the mass of oxygen in a 2.0-L bottle of air at 1.0 atm, 25°C.

A) 0.550 g
B) 2.36 g
C) 1.81 g
D) 2.62 g
E) none of these

Question 32

Calculate the density of nitrogen at STP.

A) 1.25 g/L
B) 0.625 g/L
C) 0.312 g/L
D) 1.60 g/L
E) 0.800 g/L

Question 33

It is found that 250. mL of gas at STP has a mass of 1.00

A) 14.0 g/mol
B) 89.6 g/mol
C) 22.4 g/mol
D) 28.0 g/mol
E) none of these

Question 34

The mass of 1.12 L of gas Y is found to be 6.23

A) 0.180 g/L.
B) 0.200 g/L.
C) 10.6 g/L.
D) 15.6 g/L.
E) 5.56 g/L.

Question 35

Potassium chlorate decomposes upon heating as follows:
2KClO₃(s) → 2KCl(s) + 3O₂(g)
A 2.72-g sample of KClO₃ decomposes, and the oxygen at 23.4°C and 0.935 atm is collected. What volume of oxygen gas will be collected, assuming 100% yield?

A) 2.21 mL
B) 0.577 mL
C) 0.0456 mL
D) 0.0684 mL
E) 0.866 mL

Question 36

When a mixture is prepared from 15.0 L of ammonia and 15.0 L of chlorine measured at the same conditions, these compounds react according to the following equation:
2NH₃(g) + 3Cl₂(g) → N₂(g) + 6HCl(g)
When the reaction is completed, what are the volumes of the gases (NH₃, Cl₂, N₂, and HCl, respectively)? Assume the final volumes are measured under identical conditions.

A) 0.00 L, 0.00 L, 5.00 L, and 30.0 L
B) 0.00 L, 0.00 L, 7.50 L, and 45.0 L
C) 0.00 L, 5.00 L, 7.50 L, and 45.0 L
D) 5.00 L, 0.00 L, 5.00 L, and 30.0 L
E) 0.00 L, 10.0 L, 15.0 L, and 90.0 L

Question 37

The molar mass of gas Y is

A) 89.0 g/mol.
B) 56.0 g/mol.
C) 157 g/mol.
D)140. g/mol.
E) 125 g/mol.

Question 38

If a 2.15-g sample of a gas occupies 750. mL at STP, what is the molar mass of the gas at 125°C?

A) 75.0
B) 3.07 × 10^-2
C) 64.2
D) 70.1
E) Not enough information is given.

Question 39

Four identical 1.0-L flasks contain the gases He, Cl₂, CH₄, and NH₃, each at 0°C and
1 atm pressure.
Which gas sample has the greatest number of molecules?

A) He
B) NH₃
C) Cl₂
D) CH₄
E) All the gases have the same number of molecules.

Question 40

A mixture of KCl and KClO₃ weighing 1.80 g was heated; the dry O₂ generated occupied 1.40 × 10² mL at STP. What percent of the original mixture was KClO₃? KClO₃ decomposes as follows:
2KClO₃(s) → 2KCl(s) + 3O₂(g)

A) 37.2%
B) 72.6%
C) 42.6%
D) 63.8%
E) 28.4%

Question 41

How many of the following gases at STP are less dense than air at STP?
NH₃, He, Kr, and F₂

A) 4
B) 0
C) 2
D) 1
E) 3

Question 42

A 0.234-g sample of a gas in a 275-mL container at 23.5°C exerts a pressure of 0.292 atm What is the molar mass of the gas?

A) 70.9 g/mol
B) 0.0141 g/mol
C) 5.62 g/mol
D) 32.0 g/mol
E) none of these

Question 43

The purity of a sample containing zinc and weighing 0.198 g is determined by measuring the amount of hydrogen formed when the sample reacts with an excess of hydrochloric acid. The determination shows the sample to be 84.0% zinc. What amount of hydrogen (measured at STP) was obtained?

A) 1.53 × 10²¹ atoms
B) 3.42 × 10^-3 mol
C) 0.152 L
D) 0.0330 g
E) 1.53 × 10²¹ molecules

Question 44

A 3.82-g sample of lead(II) nitrate, Pb(NO₃)₂, molar mass = 331 g/mol, is heated in an evacuated cylinder with a volume of 1.70 L. The salt decomposes when heated, according to the equation
2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g)
Assuming complete decomposition, what is the pressure in the cylinder after decomposition and cooling to a temperature of 290. K? Assume the PbO(s) takes up negligible volume.

A) 0.565 atm
B) 0.162 atm
C) 0.784 atm
D) 0.808 atm
E) 0.404 atm

Question 45

A 226.4-L cylinder contains 65.5% He(g) and 34.5% Kr(g) by mass at 27.0°C and 1.40 atm total pressure. What is the mass of He in this container?

A) 26.5 g
B) 50.3 g
C) 76.8 g
D) 559 g
E) 33.8 g

Question 46

Oxygen gas, generated by the reaction 2KClO₃(s) → 2KCl(s) + 3O₂(g), is collected over water at 27°C in a 3.72-L vessel at a total pressure of 730. torr. (The vapor pressure of H₂O at 27°C is 26.0 torr.) How many moles of KClO₃ were consumed in the reaction?

A) 0.100 mol
B) 0.210 mol
C) 0.0933 mol
D) 70.9 mol
E) 1.04 mol

Question 47

A balloon contains an anesthetic mixture of cyclopropane (C₃H₆) and oxygen (O₂) at 160 torr and 550 torr, respectively. What is the ratio of the number of moles of cyclopropane to the number of moles of oxygen?
N_cp/no₂ = ?

A) 0.29
B) ​0.77
C) ​0.23
D) ​3.4
E) ​0.26

Question 48

The oxidation of nitric oxide to nitrogen dioxide is
2NO(g) + O₂(g) → 2NO₂(g)
If 100.0 mL of NO (at STP) reacts with 400.0 mL of O₂ at STP, calculate the partial pressure of NO₂ in the final reaction mixture.

A) 0.222 atm
B) 0.286 atm
C) 0.333 atm
D) 0.250 atm
E) 1.00 atm

Question 49

A gaseous mixture containing 1.5 mol Ar and 3.5 mol CO₂ has a total pressure of 7.0 atm. What is the partial pressure of CO₂?

A) 2.4 atm
B) 3.5 atm
C) 4.9 atm
D) 1.8 atm
E) 2.1 atm

Question 50

A 275.0-mL sample of O₂ is collected over water at 60.0°C. The total pressure is 755 torr. What is the volume of the O₂ at the STP? (The vapor pressure of water at 60°C is 149 torr).

A) 244.0 mL
B) 224.0 mL
C) 180.0 mL
D) 333.0 mL
E) none of these

Question 51

When 0.72 g of a liquid is vaporized at 110°C and 0.967 atm, the gas occupies a volume of 0.559 L. The empirical formula of the gas is CH₂. What is the molecular formula of the gas?

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

Question 52

At 1000°C and 10. torr, the density of a certain element in the gaseous state is 2.9 × 10^-3 g/L. The element is

A) Ne.
B) Ar.
C) He.
D) Na.
E) Hg.

Question 53

Four identical 1.0-L flasks contain the gases He, Cl₂, CH₄, and NH₃, each at 0°C and 1 atm pressure.
For which gas do the molecules have the highest average velocity?

A) He
B) CH₄
C) NH₃
D) Cl₂
E) The molecules of all the gases have the same average velocity.

Question 54

Four identical 1.0-L flasks contain the gases He, Cl₂, CH₄, and NH₃, each at 0°C and 1 atm pressure.
For which gas are the collisions elastic?

A) He
B) Cl₂
C) CH₄
D) NH₃
E) The collisions are elastic for all the gases.

Question 55

A vessel with a volume of 10.1 L contains 3.28 g of nitrogen gas, 0.400 g of hydrogen gas, and 85.0 g of argon gas. At 26.0°C, what is the pressure in the vessel?

A) 215 atm
B) 0.516 atm
C) 8.99 × 10⁴ atm
D) 5.94 atm
E) 3.08 atm

Question 56

A 130.-mL sample of gas is collected over water at 22°C and 753 torr. What is the volume of the dry gas at STP? (The vapor pressure of water at 22°C is 20. torr.)

A) 111 mL
B) 135 mL
C)130. mL
D) 119 mL
E) none of these

Question 57

A 1.00-g sample of a gaseous compound of boron and hydrogen occupies 0.820 L at 1.00 atm and 3°C. What is the molecular formula for the compound?

A) B₂H₆
B) B₄H₁₀
C) B₅H₁₄
D) B₃H₁₂
E) BH₃

Question 58

A 250.0-L cylinder contains 65.0% He(g) and 35.0% Kr(g) by mass at 25.0°C and 1.35 atm total pressure. What is the partial pressure of He in this container?

A) 0.675 atm
B) 0.878 atm
C) 1.32 atm
D) 1.35 atm
E) 0.473 atm

Question 59

Consider three 1.0-L flasks at STP. Flask A contains N₂ gas, flask B contains Kr gas, and flask C contains H₂ gas.In which flask do the gas particles have the lowest average kinetic energy?

A) flask B
B) The gas particles in all of the flasks have the same average kinetic energy.
C) The gas particles in two of the flasks have the same average kinetic energy.
D) flask C
E) flask A

Question 60

Three 1.00-L flasks at 25°C and 725 torr contain the gases CH₄ (flask A), CO₂ (flask B), and C₂H₆ (flask C).In which single flask do the molecules have the greatest mass, the greatest average velocity, and the highest kinetic energy?

A) flask A
B) flask B
C) flask C
D) all
E) none

Question 61

Four identical 1.0-L flasks contain the gases He, Cl₂, CH₄, and NH₃, each at 0°C and 1 atm pressure.
For which gas do the molecules have the smallest average kinetic energy?

A) He
B) CH₄
C) NH₃
D) Cl₂
E) The molecules of all the gases have the same average kinetic energy.

Question 62

The kinetic-molecular theory of gases does not assume that

A) gas particles are very small compared to the average distance between the particles.
B) gas particles collide with the walls of their container in elastic collisions.
C) the average velocity of gas particles is directly proportional to the absolute temperature.
D) gases are made up of tiny particles in constant chaotic motion.
E) All of these are correct.

Question 63

Samples of the gases H₂(g) and SO₂(g) have equal masses and are at the same temperature and pressure. Calculate the following:
The ratio of average kinetic energies per molecule (H₂:SO₂)

A) 0.18
B) 5.6
C) 180
D) 1.0
E) 32

Question 64

Consider three 1-L flasks at the same temperature and pressure. Flask A contains CO gas, flask B contains N₂ gas, and flask C contains O₂ gas.In which flask do the molecules have the greatest momentum per impact?

A) The molecules in all the flasks have the same momentum per impact.
B) flask C
C) The molecules in two of the flasks have the same momentum per impact.
D) flask A
E) flask B

Question 65

Calculate the temperature at which the average velocity of Ar(g) equals the average velocity of Ne(g) at 25°C.

A) 25°C
B) 151°C
C) 317°C
D) 49.5°C
E) none of these

Question 66

Which statement about kinetic energy (K.E.) is true?

A) The K.E. of a body will double if its velocity doubles.
B) As the velocity of a body increases, its K.E. decreases.
C) The K.E. of a body is independent of its mass.
D) All objects moving with the same velocity have the same K.E.
E) None of these statements is true.

Question 67

Consider two 1.0-L containers, one containing He(g) at 2.50 atm and 24°C and the other containing Ar(g) at 5.00 atm and 48°C.
Calculate the ratio of average velocities (He:Ar).

A) 0.108
B) 4.98
C) 0.200
D) 9.22
E) none of these

Question 68

Samples of the gases H₂(g) and SO₂(g) have equal masses and are at the same temperature and pressure. Calculate the following:
The ratio of the forces per wall impact .

A) 5.6
B) 0.18
C) 1.0
D) 32
E) 180

Question 69

The root-mean-square velocity of a gas in a closed container of fixed volume is increased from 345 m/s to 690 m/s. Which one of the following statements might explain correctly how this change was accomplished?

A) By pumping in more gas at constant temperature, the pressure was quadrupled.
B) By heating the gas, the temperature was doubled.
C) By heating the gas, the pressure was quadrupled.
D) By pumping out 75% of the gas at constant temperature, the pressure was decreased to 25% of its original value.
E) None of these statements correctly explains the change.

Question 70

Consider the following gas samples:
​
​
Which one of the following statements is false?

A) Assuming identical intermolecular forces in the two samples, sample A should be more nearly ideal than sample B.
B) The root-mean-square velocity of molecules in sample A is twice as large as the root-mean-square velocity of molecules in sample B.
C) The average kinetic energy of the molecules in sample A is twice the average kinetic energy of the molecules in sample B.
D) The fraction of molecules in sample A having a kinetic energies greater than some high fixed value is larger than the fraction of molecules in sample B having kinetic energies greater than that same high fixed value.
E) The volume of sample A is twice the volume of sample B.

Question 71

The root-mean-square velocity of N₂ gas at 35°C is

A) 52.0 m/s.
B) 177 m/s.
C) 5.58 m/s
D) 524 m/s.
E) 16.6 m/s

Question 72

At 200 K, the molecules or atoms of an unknown gas, X, have an average velocity equal to that of Ar atoms at 400 K. What is X? (Assume ideal behavior.)

A) CO
B) F₂
C) He
D) HF
E) HBr

Question 73

Which of the following statements is true concerning ideal gases?

A) The temperature of the gas sample is directly related to the average velocity of the gas particles.
B) At STP, 1.0 L of Ar(g) contains about twice the number of atoms as 1.0 L of Ne(g) because the molar mass of Ar is about twice that of Ne.
C) A gas exerts pressure as a result of the collisions of the gas molecules with the walls of the container.
D) The gas particles in a sample exert attraction on one another.
E) All of these statements are false.

Question 74

Under which of the following conditions does a gas behave most ideally?

A) STP
B) P = 2.0 atm, T = -100.0°C
C) P = 0.50 atm, T = 0.0°C
D) P = 1.0 atm, T = 100.0°C
E) P = 0.50 atm, T = 100.0°C

Question 75

Calculate the temperature at which the average kinetic energy of O₂ gas is twice that of He gas at 10.0°C.

A) 293°C
B) 20.0°C
C) 160.0°C
D) 2.50°C
E) 10.0°C

Question 76

Calculate the following ratios for a gas at Kelvin temperatures T₁ and T₂ where T₂ = 2T₁.Average kinetic energy at T₁ : Average kinetic energy at T₂

A) 2.0
B) 0.50
C) 0.71
D) 1.0
E) 1.4

Question 77

Consider separate samples of Ar(g) and Ne(g). For what ratio of absolute temperatures (Ne:Ar) are the average kinetic energies equal?

A) 1.41
B) 0.505
C) 1.98
D) 1.00
E) none of these

Question 78

Calculate the ratio of the change in momentum per wall impact for Ar(g) to that for He(g) if the gases are at the same temperature and pressure.

A) 0.316
B) 3.16
C) 9.98
D) 0.100
E) none of these

Question 79

Samples of the gases H₂(g) and SO₂(g) have equal masses and are at the same temperature and pressure. Calculate the following:
The ratio of the root-mean-square velocities .

A) 180
B) 32
C) 0.18
D) 1.0
E) 5.6

Question 80

Consider two 1.0-L containers, one containing He(g) at 2.50 atm and 24°C and the other containing Ar(g) at 5.00 atm and 48°C.
Calculate the ratio of impacts with the wall per second (He:Ar).

A) 9.22
B) 1.64
C) 4.98
D) 6.25
E) none of these