Question 1

A sample container of carbon monoxide occupies a volume of 435 mL at a pressure of 785 torr and a temperature of 298 K. What would its temperature be if the volume were changed to 265 mL at a pressure of 785 torr?

Accepted Answer

A)   182 K
B)   298 K
C)   387 K
D)   489 K
E)   538 K

Question 2

Ima Chemist found the density of Freon-11 (CFCl3)  to be 5.58 g/L under her experimental conditions. Her measurements showed that the density of an unknown gas was 4.38 g/L under the same conditions. What is the molar mass of the unknown?

Accepted Answer

A)   96.7 g/mol
B)   108 g/mol
C)   127 g/mol
D)   165 g/mol
E)   175 g/mol

Question 3

For a gas obeying Charles's Law, a plot of V versus 1/T will give a straight line passing through the origin.

Accepted Answer

A) True 
 B)False

Question 4

"The volume of an ideal gas is directly proportional to the number of moles of the gas at constant temperature and pressure" is a statement of _____________ Law.

Accepted Answer

A)   Charles's
B)   Boyle's
C)   Amontons's
D)   Avogadro's
E)   Dalton's

Question 5

Small quantities of hydrogen can be prepared by the addition of hydrochloric acid to zinc. A sample of 195 mL of hydrogen was collected over water at 25°C and 753 torr. What mass of hydrogen was collected? (Pwater = 24 torr at 25°C)

Accepted Answer

A)   0.00765 g
B)   0.0154 g
C)   0.0159 g
D)   0.0164 g
E)   0.159 g

Question 6

At moderate pressures (~ 200 atm) , the measured pressure exerted by CO2 gas is less than that predicted by the ideal gas equation. This is mainly because

Accepted Answer

A)   such high pressures cannot be accurately measured.
B)   CO2 will condense to a liquid at 200 atm pressure.
C)   gas phase collisions prevent CO2 molecules from colliding with the walls of the container.
D)   of attractive intermolecular forces between CO2 molecules.
E)   the volume occupied by the CO2 molecules themselves becomes significant.

Question 7

The most probable speed of an oxygen molecule in the gas phase at room temperature is 450 m/s. The root-mean-square speed (urms)  is therefore

Accepted Answer

A)   equal to 450 m/s.
B)   slightly less than 450 m/s.
C)   much less than 450 m/s.
D)   slightly greater than 450 m/s.
E)   much greater than 450 m/s.

Question 8

According to the postulates of kinetic-molecular theory, the average kinetic energy of gas molecules is proportional to the absolute temperature.

Accepted Answer

A) True 
 B)False

Question 9

"The pressure of an ideal gas is directly proportional to its absolute temperature at constant volume and number of moles" is a statement of ________________ Law.

Accepted Answer

A)   Charles's
B)   Boyle's
C)   Amontons's
D)   Avogadro's
E)   Gay-Lussac's

Question 10

Mineral oil can be used in place of mercury in manometers when small pressure changes are to be measured. What is the pressure of an oxygen sample in mm of mineral oil if its pressure is 28.5 mm Hg? (d of mineral oil = 0.88 g/mL; d of Hg = 13.5 g/mL)

Accepted Answer

A)   1.9 mm mineral oil
B)   15 mm mineral oil
C)   32 mm mineral oil
D)   380 mm mineral oil
E)   440 mm mineral oil

Question 11

Assuming ideal behavior, what is the density of argon gas at STP, in g/L?

Accepted Answer

A)   0.0176 g/L
B)   0.0250 g/L
C)   0.0561 g/L
D)   1.78 g/L
E)   181. g/L

Question 12

A 250.0-mL sample of ammonia, NH3(g) , exerts a pressure of 833 torr at 42.4°C. What mass of ammonia is in the container?

Accepted Answer

A)   0.0787 g
B)   0.180 g
C)   8.04 g
D)   17.0 g
E)   59.8 g

Question 13

The rate of diffusion of a gas is inversely proportional to its molar mass.

Accepted Answer

A) True 
 B)False

Question 14

What are the conditions of STP?

Accepted Answer

A)   0 K and l atm
B)   273.15 K and 760 torr
C)   0°C and 760 atm
D)   273.15°C and 760 torr
E)   None of these choices are correct.

Question 15

A flask containing neon gas is connected to an open-ended mercury manometer. The open end is exposed to the atmosphere, where the prevailing pressure is 745 torr. The mercury level in the open arm is 50. mm below that in the arm connected to the flask of neon. What is the neon pressure, in torr?

Accepted Answer

A)   -50. torr
B)   50. torr
C)   695 torr
D)   795 torr
E)   None of these choices are correct.

Question 16

According to the postulates of kinetic-molecular theory, the molecules of all gases at a given temperature have the same average speed.

Accepted Answer

A) True 
 B)False

Question 17

At very high pressures (~ 1000 atm) , the measured pressure exerted by real gases is greater than that predicted by the ideal gas equation. This is mainly because

Accepted Answer

A)   such high pressures cannot be accurately measured.
B)   real gases will condense to form liquids at 1000 atm pressure.
C)   gas phase collisions prevent molecules from colliding with the walls of the container.
D)   of attractive intermolecular forces between gas molecules.
E)   the volume occupied by the gas molecules themselves becomes significant.

Question 18

An unknown liquid is vaporized in a 273-mL flask by immersion in a water bath at 99°C. The barometric pressure is 753 torr. If the mass of the vapor retained in the flask is 1.362 g, what is its molar mass?

Accepted Answer

A)   20.4 g/mol
B)   40.9 g/mol
C)   112 g/mol
D)   154 g/mol
E)   184 g/mol

Question 19

A ballerina weighs 103 lbs and is up on her toes with only 10.0 cm2 of her slippers in contact with the floor. What pressure is she exerting on the floor?

Accepted Answer

A)   4.59 × 105 Pa
B)   4.59 × 103 Pa
C)   4.59 × 101 Pa
D)   4.59 × 10-1 Pa
E)   4.59 × 10-3 Pa

Question 20

A sample of an ideal gas has its volume doubled while its temperature remains constant. If the original pressure was 100 torr, what is the new pressure?

Accepted Answer

A)   10 torr
B)   50 torr
C)   100 torr
D)   200 torr
E)   1000 torr

Exam 5: Gases and the Kinetic-Molecular Theory

Ima Chemist found the density of Freon-11 (CFCl3) to be 5.58 g/L under her experimental conditions. Her measurements showed that the density of an unknown gas was 4.38 g/L under the same conditions. What is the molar mass of the unknown?

Correct AnswerverifiedShow Answer

At very high pressures (~ 1000 atm) , the measured pressure exerted by real gases is greater than that predicted by the ideal gas equation. This is mainly because

Correct AnswerverifiedShow Answer

According to the postulates of kinetic-molecular theory, the molecules of all gases at a given temperature have the same average speed.

Correct AnswerverifiedShow Answer

An unknown liquid is vaporized in a 273-mL flask by immersion in a water bath at 99°C. The barometric pressure is 753 torr. If the mass of the vapor retained in the flask is 1.362 g, what is its molar mass?

Correct AnswerverifiedShow Answer

According to the postulates of kinetic-molecular theory, the average kinetic energy of gas molecules is proportional to the absolute temperature.

Correct AnswerverifiedShow Answer

"The pressure of an ideal gas is directly proportional to its absolute temperature at constant volume and number of moles" is a statement of ________________ Law.

Correct AnswerverifiedShow Answer

The most probable speed of an oxygen molecule in the gas phase at room temperature is 450 m/s. The root-mean-square speed (urms) is therefore

Correct AnswerverifiedShow Answer

The rate of diffusion of a gas is inversely proportional to its molar mass.

Correct AnswerverifiedShow Answer

"The volume of an ideal gas is directly proportional to the number of moles of the gas at constant temperature and pressure" is a statement of _____________ Law.

Correct AnswerverifiedShow Answer

What are the conditions of STP?

Correct AnswerverifiedShow Answer

A sample container of carbon monoxide occupies a volume of 435 mL at a pressure of 785 torr and a temperature of 298 K. What would its temperature be if the volume were changed to 265 mL at a pressure of 785 torr?

Correct AnswerverifiedShow Answer

A 250.0-mL sample of ammonia, NH3(g) , exerts a pressure of 833 torr at 42.4°C. What mass of ammonia is in the container?

Correct AnswerverifiedShow Answer

Assuming ideal behavior, what is the density of argon gas at STP, in g/L?

Correct AnswerverifiedShow Answer

At moderate pressures (~ 200 atm) , the measured pressure exerted by CO2 gas is less than that predicted by the ideal gas equation. This is mainly because

Correct AnswerverifiedShow Answer

A flask containing neon gas is connected to an open-ended mercury manometer. The open end is exposed to the atmosphere, where the prevailing pressure is 745 torr. The mercury level in the open arm is 50. mm below that in the arm connected to the flask of neon. What is the neon pressure, in torr?

Correct AnswerverifiedShow Answer

Mineral oil can be used in place of mercury in manometers when small pressure changes are to be measured. What is the pressure of an oxygen sample in mm of mineral oil if its pressure is 28.5 mm Hg? (d of mineral oil = 0.88 g/mL; d of Hg = 13.5 g/mL)

Correct AnswerverifiedShow Answer

For a gas obeying Charles's Law, a plot of V versus 1/T will give a straight line passing through the origin.

Correct AnswerverifiedShow Answer

A ballerina weighs 103 lbs and is up on her toes with only 10.0 cm2 of her slippers in contact with the floor. What pressure is she exerting on the floor?

Correct AnswerverifiedShow Answer

Small quantities of hydrogen can be prepared by the addition of hydrochloric acid to zinc. A sample of 195 mL of hydrogen was collected over water at 25°C and 753 torr. What mass of hydrogen was collected? (Pwater = 24 torr at 25°C)

Correct AnswerverifiedShow Answer

A sample of an ideal gas has its volume doubled while its temperature remains constant. If the original pressure was 100 torr, what is the new pressure?

Correct AnswerverifiedShow Answer

Ima Chemist found the density of Freon-11 (CFCl₃) to be 5.58 g/L under her experimental conditions. Her measurements showed that the density of an unknown gas was 4.38 g/L under the same conditions. What is the molar mass of the unknown?

Correct Answer
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The most probable speed of an oxygen molecule in the gas phase at room temperature is 450 m/s. The root-mean-square speed (u_rms) is therefore

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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A 250.0-mL sample of ammonia, NH₃(g) , exerts a pressure of 833 torr at 42.4°C. What mass of ammonia is in the container?

Correct Answer
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Correct Answer
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At moderate pressures (~ 200 atm) , the measured pressure exerted by CO₂ gas is less than that predicted by the ideal gas equation. This is mainly because

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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A ballerina weighs 103 lbs and is up on her toes with only 10.0 cm² of her slippers in contact with the floor. What pressure is she exerting on the floor?

Correct Answer
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Small quantities of hydrogen can be prepared by the addition of hydrochloric acid to zinc. A sample of 195 mL of hydrogen was collected over water at 25°C and 753 torr. What mass of hydrogen was collected? (P_water = 24 torr at 25°C)

Correct Answer
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Correct Answer
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