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Exam 5: Gases

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Question 1

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Methane gas,CH₄,effuses through a barrier at a rate of 0.568 mL/minute.If an unknown gas effuses through the same barrier at a rate of 0.343 mL/minute,what is the molar mass of the gas?

A) 20.8 g/mol
B) 28.0 g/mol
C) 32.0 g/mol
D) 43.9 g/mol
E) 64.0 g/mol

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Question 2

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What volume does 22.4 moles of hydrogen gas occupy at 0°C and 1.00 atm?

A) 0.0821 L
B) 1.00 L
C) 22.4 L
D) 184 L
E) 502 L

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Question 3

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An unknown gas contains 85.6% C and 14.4% H.At 0.455 atm and 425 K,the gas has a density of 0.549 g/L.What is the molecular formula of the gas?

A tightly sealed 4.0-L flask contains 884 mm Hg of N₂ at 94.0°C.The flask is cooled until the pressure is reduced to 442 mm Hg.What is the temperature of the gas?

A sample of carbon dioxide is collected over water at 25°C (vapor pressure H₂O(l) = 23.8 mm Hg) .The CO₂ and water vapor occupy a volume of 1.80 L at a pressure of 783.0 mm Hg.What mass of CO₂ is present?

Water can be decomposed by electrolysis to hydrogen gas and oxygen gas.What mass of water must decompose to yield 24.0 L of oxygen gas at 1.00 atm and 25°C? 2H₂O(l) → 2H₂(g) + O₂(g)

A volatile compound with a mass of 0.8822 grams is placed in an evacuated 0.250 L flask.The flask is heated to evaporate the compound.At 99°C,the pressure in the flask is 1.25 atm.What is the molar mass of the compound?

At 21°C,a gas cylinder containing nitrogen has an internal volume and pressure of 46.6 L and 1.50 × 10² atm.What mass of nitrogen gas is contained in the cylinder?

The molar masses of helium and oxygen are 4.0 g/mol and 16 g/mol,respectively.At the same temperature and pressure,1 mole of helium will occupy

At 1.00 km above sea level,the atmospheric pressure is 675 mm Hg and the temperature is 282 K.If nitrogen comprises 78.1% (mole percent) of air,what is the density of nitrogen at this height?

A volume of 3.0 L of butane is burned in excess oxygen.Balance the chemical equation below and determine how many total liters of gases are produced.Assume that both the reactant and product temperature is 500 K and the pressure of the system remains constant at 1.0 atm. C₄H₁₀(g) + O₂(g) → CO₂(g) + H₂O(g)

Calculate the density (in g/L) of CH₄(g) at 75°C and 2.1 atm.(R = 0.08206 L · atm/mol · K)

In an experiment,argon is allowed to effuse through a tiny opening into an evacuated 5.00 × 10² mL flask for 30.0 seconds,at which point the pressure in the flask is found to be 15.0 mm Hg.The experiment is repeated using an unknown gas at the same temperature and pressure.After 30.0 seconds,the pressure is found to be 47.4 mm Hg.What is the molar mass of the gas?

A balloon is filled with 1.50 L of helium gas at sea level,1.00 atm and 32°C.The balloon is released and it rises to an altitude of 30,000 ft.If the pressure at this altitude is 228 mm Hg and the temperature is −45°C,what is the volume of the balloon?

At 338 mm Hg and 72°C,a sample of carbon monoxide gas occupies a volume of 0.225 L.The gas is transferred to a 1.50-L flask and the temperature is reduced to -15°C.What is the pressure of the gas in the flask?

Place the following units of pressure in order from lowest to highest pressure.

Avogadro's law states that

Water can be decomposed by electrolysis to hydrogen gas and oxygen gas.If 2.33 g of water is decomposed to H₂(g) and O₂(g) and the gases are collected in a 1.00 L flask over water at 25°C (vapor pressure H₂O(l) = 23.8 mm Hg) ,what is the pressure in the flask?

If the volume of a confined gas is expanded to four times the original volume while its temperature remains constant,what change will be observed?

A balloon is filled with He gas to a volume of 2.10 L at 35°C.The balloon is placed in liquid nitrogen until its temperature reaches -196°C.Assuming the pressure remains constant,what is the volume of the cooled balloon?