Question 1

If equal masses of O₂(g)and HBr(g)are in separate containers of equal volume and temperature, which one of these statements is true? A)The pressure in the O₂ container is greater than that in the HBr container. B)There are more HBr molecules than O₂ molecules. C)The average velocity of the O₂ molecules is less than that of the HBr molecules. D)The average kinetic energy of HBr molecules is greater than that of O₂ molecules. E)The pressures of both gases are the same.

Accepted Answer

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Question 2

Determine the pressure of the gas trapped in the apparatus shown below when the atmospheric pressure is 695 mmHg. 
A)45 mmHg
B)650 mmHg
C)695 mmHg
D)740 mmHg
E)760 mmHg

Accepted Answer

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Question 3

What mass of KClO₃ must be decomposed to produce 126 L of oxygen gas at 133°C and 0.880 atm? (The other reaction product is solid KCl.) A)24.6 g B)70.8 g C)272 g D)408 g E)612 g

Accepted Answer

Using the ideal gas law, calculate moles of O2: PV = nRT. Convert temperature to Kelvin and solve for n. Then use stoichiometry from the balanced equation 2 KClO3 → 2 KCl + 3 O2 to find moles of KClO3. Finally, convert moles of KClO3 to grams.

Question 4

Which statement is false?
A)The average kinetic energies of molecules from samples of different "ideal" gases is the same at the same temperature.
B)The molecules of an ideal gas are relatively far apart.
C)All molecules of an ideal gas have the same kinetic energy at constant temperature.
D)Molecules of a gas undergo many collisions with each other and the container walls.
E)Molecules of greater mass have a lower average speed than those of less mass at the same temperature.

Accepted Answer

The kinetic energy of molecules in an ideal gas is directly proportional to their temperature, but not all molecules have the same kinetic energy at the same temperature. The distribution of kinetic energies follows a Maxwell-Boltzmann distribution, meaning that some molecules will have higher or lower kinetic energies than others at the same temperature.

Question 5

A spacecraft is filled with 0.500 atm of N₂ and 0.500 atm of O₂.Suppose a micrometeor strikes this spacecraft and puts a very small hole in it's side.Under these circumstances, A)O₂ is lost from the craft 6.9% faster than N₂ is lost. B)O₂ is lost from the craft 14% faster than N₂ is lost. C)N₂ is lost from the craft 6.9% faster than O₂ is lost. D)N₂ is lost from the craft 14% faster than O₂ is lost. E)N₂ and O₂ are lost from the craft at the same rate.

Accepted Answer

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Question 6

A spacecraft is filled with 0.500 atm of O₂ and 0.500 atm of He.If there is a very small hole in the side of this craft such that gas is lost slowly into outer space, A)He is lost 2.8 times faster than O₂ is lost. B)He is lost 8 times faster than O₂ is lost. C)He is lost twice as fast as O₂ is lost. D)O₂ is lost 2.8 times faster than He is lost. E)O₂ is lost 8 times faster than He is lost.

Accepted Answer

The rate of effusion (loss of gas through a small opening) is directly proportional to the velocity of the gas molecules, which in turn is related to the square root of the molar mass of the gas. He has a molar mass of 4 g/mol, and O₂ has a molar mass of approximately 32 g/mol (assuming it is sulfur hexafluoride). Therefore, the ratio of the effusion rates of He to O₂ is: $\sqrt{\frac{4}{32}} \approx 0.3536$ or He is lost approximately 2.8 times faster than O₂. Therefore, the correct answer is (A).

Question 7

Liquid nitrogen has a density of 0.807 g/mL at -195.8 °C.If 1.00 L of N₂(l)is allowed to warm to 25°C at a pressure of 1.00 atm, what volume will the gas occupy? (R = 0.08206 L.atm/K.mol) A)59.1 L B)182 L C)705 L D)1.41 × 10³ L E)1.97 × 10⁴ L

Accepted Answer

Using the ideal gas law, PV=nRT, we can solve for the final volume V. We first need to find the number of moles of gas, which can be found using the density and the molar mass of nitrogen (28.02 g/mol):

density = mass/volume
volume = mass/density = (1000 mL) * (0.807 g/mL) = 807 g = 0.807 kg
n = mass/molar mass = 0.807 kg / 28.02 g/mol = 0.0288 mol

Next, we can use the initial and final temperatures in Kelvin (77.35 K and 298 K, respectively), and the given pressure of 1.00 atm:

V = nRT/P = (0.0288 mol)*(0.08206 L*atm/mol*K)*(298 K)/(1.00 atm) = 0.705 L

Therefore, the gas will occupy a volume of 0.705 L at 25°C and 1.00 atm.

Question 8

What is the pressure of the gas trapped in the apparatus shown below when the atmospheric pressure is 720 mmHg? 
A)12 mmHg
B)708 mmHg
C)720 mmHg
D)732 mmHg
E)760 mmHg

Accepted Answer

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Question 9

The molecules of different samples of an ideal gas have the same average kinetic energies, at the same
A)pressure.
B)temperature.
C)volume.
D)density.

Accepted Answer

The average kinetic energy of gas molecules is directly proportional to the temperature of the gas. Therefore, if two samples of an ideal gas have the same average kinetic energy, they must be at the same temperature. The pressure, volume, and density of the gas can vary between the two samples as long as the temperature remains constant.

Question 10

For a substance that remains a gas under the conditions listed, deviation from the ideal gas law would be most pronounced at
A)100°C and 2.0 atm.
B)0°C and 2.0 atm.
C)-100°C and 2.0 atm.
D)-100°C and 4.0 atm.
E)100°C and 4.0 atm.

Accepted Answer

According to the van der Waals equation, deviation from ideal behavior is most pronounced when both pressure and temperature are low. Choice D has the lowest temperature and a relatively high pressure, making it the best option.

Question 11

A sample of mercury(II)oxide is placed in a 5.00 L evacuated container and heated until it decomposes entirely to mercury metal and oxygen gas.The container is then cooled to 25°C.One now finds that the gas pressure inside the container is 1.73 atm.What mass of mercury(II)oxide was originally placed into the container?
A)1.51 g
B)45.6g
C)76.6 g
D)913 g
E)153 g

Accepted Answer

Using the ideal gas law, PV = nRT, we can calculate the moles of oxygen gas produced. With P = 1.73 atm, V = 5.00 L, R = 0.0821 L·atm/mol·K, and T = 298 K, we find n = 0.353 mol of O2. Since the decomposition of HgO produces O2 in a 2:1 ratio, 0.706 mol of HgO was decomposed. The molar mass of HgO is 216.59 g/mol, so the mass of HgO is 0.706 mol × 216.59 g/mol = 153 g.

Question 12

Deviations from the ideal gas law are greater at
A)low temperatures and low pressures.
B)low temperatures and high pressures.
C)high temperatures and high pressures.
D)high temperatures and low pressures.

Accepted Answer

Deviations from the ideal gas law are greater at low temperatures and high pressures because at these conditions, the size of gas molecules becomes significant and intermolecular forces play a more dominant role, leading to deviations from the ideal gas behavior.

Question 13

A method of removing CO₂ from a spacecraft is to allow the CO₂ to react with sodium hydroxide.(The products of the reaction are sodium carbonate and water.)What volume of carbon dioxide at 25°C and 749 mmHg can be removed per kilogram of sodium hydroxide that reacts? A)276 L B)284 L C)301 L D)310 L E)620 L

Accepted Answer

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Question 14

When active metals such as magnesium are immersed in acid solution, hydrogen gas is evolved.Calculate the volume of H₂(g)at 30.1°C and 0.85 atm that can be formed when 275 mL of 0.725 M HCl solution reacts with excess Mg to give hydrogen gas and aqueous magnesium chloride. A)3.4 × 10^-3 L B)2.2 L C)2.9 L D)5.8 L E)11.7 L

Accepted Answer

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Question 15

Which gas has molecules with the greatest average molecular speed at 25°C? A)CH₄ B)Kr C)N₂ D)CO₂ E)Ar

Accepted Answer

The average molecular speed of a gas is inversely proportional to the square root of its molar mass. CH₄ has the lowest molar mass among the given gases, so it has the greatest average molecular speed at 25°C.

Question 16

Samples of the following volatile liquids are opened simultaneously at one end of a room.If you are standing at the opposite end of this room, which species would you smell first? (Assume that your nose is equally sensitive to all these species.) A)ethyl acetate (CH₃COOC₂H₅) B)camphor (C₁₀H₁₆O) C)diethyl ether (C₂H₅OC₂H₅) D)naphthalene (C₁₀H₈) E)pentanethiol (C₅H₁₁SH)

Accepted Answer

Diethyl ether has the lowest boiling point and highest vapor pressure, making it the most volatile and therefore the first to reach the opposite end of the room.

Question 17

Which of these gas molecules have the highest average kinetic energy at 25°C? A)H₂ B)O₂ C)N₂ D)Cl₂ E)All the gases have the same average kinetic energy.

Accepted Answer

The average kinetic energy of a gas molecule depends only on the temperature of the gas, not on the identity of the gas molecule. Therefore, all gases have the same average kinetic energy at 25°C.

Question 18

The mole fraction of oxygen molecules in dry air is 0.2095.What volume of dry air at 1.00 atm and 25°C is required for burning 1.00 L of octane (C₈H₁₈, density = 0.7025 g/mL)completely, yielding carbon dioxide and water? A)150 L B)367 L C)718 L D)1880 L E)8970 L

Accepted Answer

The answer of The mole fraction of oxygen molecules in...

Question 19

The mole fraction of oxygen molecules in dry air is 0.2095.What volume of dry air at 1.00 atm and 25°C is required for burning 1.00 L of hexane (C₆H₁₄, density = 0.660 g/mL)completely, yielding carbon dioxide and water? A)187 L B)712 L C)894 L D)1780 L E)8490 L

Accepted Answer

The answer of The mole fraction of oxygen molecules in...

Question 20

Calculate the volume of H₂(g)at 273 K and 2.00 atm that will be formed when 275 mL of 0.725 M HCl solution reacts with excess Mg to give hydrogen gas and aqueous magnesium chloride. A)0.56 L B)1.12 L C)2.23 L D)3.54 L E)4.47 L

Accepted Answer

1. Write the balanced chemical equation: 2HCl(aq) + Mg(s) -> H2(g) + MgCl2(aq) 2. Use stoichiometry to determine the amount of hydrogen gas produced: From the equation, 2 moles of HCl react with 1 mole of Mg to produce 1 mole of H2 gas. We know the initial volume of HCl solution is 275 mL = 0.275 L, and the concentration is 0.725 M. Thus, the number of moles of HCl present in the solution is: 0.725 mol/L x 0.275 L = 0.1994 mol This means 0.0997 mol of H2 gas will be produced. 3. Use the ideal gas law to determine the volume of H2 gas at STP: PV = nRT where P = 2.00 atm, V = ?, n = 0.0997 mol, R = 0.0821 L·atm/mol·K (universal gas constant), and T = 273 K. Solving for V, we get: V = nRT/P = (0.0997 mol)(0.0821 L·atm/mol·K)(273 K)/(2.00 atm) = 1.12 L Therefore, the volume of H₂(g) at 273 K and 2.00 atm that will be formed is 1.12 L. The correct answer is (B).

Quiz 5: Gases

If equal masses of O₂(g) and HBr(g) are in separate containers of equal volume and temperature, which one of these statements is true?

Determine the pressure of the gas trapped in the apparatus shown below when the atmospheric pressure is 695 mmHg.

What mass of KClO₃ must be decomposed to produce 126 L of oxygen gas at 133°C and 0.880 atm? (The other reaction product is solid KCl.)

Which statement is false?

A spacecraft is filled with 0.500 atm of N₂ and 0.500 atm of O₂.Suppose a micrometeor strikes this spacecraft and puts a very small hole in it's side.Under these circumstances,

A spacecraft is filled with 0.500 atm of O₂ and 0.500 atm of He.If there is a very small hole in the side of this craft such that gas is lost slowly into outer space,

Liquid nitrogen has a density of 0.807 g/mL at -195.8 °C.If 1.00 L of N₂(l) is allowed to warm to 25°C at a pressure of 1.00 atm, what volume will the gas occupy? (R = 0.08206 L.atm/K.mol)

What is the pressure of the gas trapped in the apparatus shown below when the atmospheric pressure is 720 mmHg?

The molecules of different samples of an ideal gas have the same average kinetic energies, at the same

For a substance that remains a gas under the conditions listed, deviation from the ideal gas law would be most pronounced at

Deviations from the ideal gas law are greater at

A method of removing CO₂ from a spacecraft is to allow the CO₂ to react with sodium hydroxide.(The products of the reaction are sodium carbonate and water.) What volume of carbon dioxide at 25°C and 749 mmHg can be removed per kilogram of sodium hydroxide that reacts?

When active metals such as magnesium are immersed in acid solution, hydrogen gas is evolved.Calculate the volume of H₂(g) at 30.1°C and 0.85 atm that can be formed when 275 mL of 0.725 M HCl solution reacts with excess Mg to give hydrogen gas and aqueous magnesium chloride.

Which gas has molecules with the greatest average molecular speed at 25°C?

Samples of the following volatile liquids are opened simultaneously at one end of a room.If you are standing at the opposite end of this room, which species would you smell first? (Assume that your nose is equally sensitive to all these species.)

Which of these gas molecules have the highest average kinetic energy at 25°C?

The mole fraction of oxygen molecules in dry air is 0.2095.What volume of dry air at 1.00 atm and 25°C is required for burning 1.00 L of octane (C₈H₁₈, density = 0.7025 g/mL) completely, yielding carbon dioxide and water?

The mole fraction of oxygen molecules in dry air is 0.2095.What volume of dry air at 1.00 atm and 25°C is required for burning 1.00 L of hexane (C₆H₁₄, density = 0.660 g/mL) completely, yielding carbon dioxide and water?

Calculate the volume of H₂(g) at 273 K and 2.00 atm that will be formed when 275 mL of 0.725 M HCl solution reacts with excess Mg to give hydrogen gas and aqueous magnesium chloride.

Quiz 5: Gases

If equal masses of O2(g) and HBr(g) are in separate containers of equal volume and temperature, which one of these statements is true?

Determine the pressure of the gas trapped in the apparatus shown below when the atmospheric pressure is 695 mmHg.

What mass of KClO3 must be decomposed to produce 126 L of oxygen gas at 133°C and 0.880 atm? (The other reaction product is solid KCl.)

Which statement is false?

A spacecraft is filled with 0.500 atm of N2 and 0.500 atm of O2.Suppose a micrometeor strikes this spacecraft and puts a very small hole in it's side.Under these circumstances,

A spacecraft is filled with 0.500 atm of O2 and 0.500 atm of He.If there is a very small hole in the side of this craft such that gas is lost slowly into outer space,

Liquid nitrogen has a density of 0.807 g/mL at -195.8 °C.If 1.00 L of N2(l) is allowed to warm to 25°C at a pressure of 1.00 atm, what volume will the gas occupy? (R = 0.08206 L.atm/K.mol)