Question 1

A compound composed of carbon, hydrogen, and chlorine effuses through a pinhole 0.411 times as fast as neon. Select the correct molecular formula for the compound. A)CHCl ₃ B)CH ₂Cl ₂ C)C ₂H ₂Cl ₂ D)C ₂H ₃Cl E)CCl ₄

Accepted Answer

The molar mass of neon is 20.2 g/mol. The molar mass of the compound is 20.2 g/mol * 0.411 = 8.3 g/mol. The molecular formula of the compound is CHCl3.

Question 2

Helium gas is being pumped into a rigid container at a constant temperature. As a result, the pressure of helium in the container is increasing. Select the one correct statement below.
A)As the pressure increases, helium atoms move faster, on average.
B)As the pressure increases, helium atoms move more slowly, on average.
C)As the pressure increases, the volume of the container must decrease.
D)As the pressure increases, helium atoms stay closer to the wall of the container, on average.
E)As the pressure increases, there are more collisions of helium atoms with the container wall.

Accepted Answer

As the pressure of helium in the container increases, the number of collisions of helium atoms with the container wall also increases. This is because the gas molecules are colliding with each other more frequently, which in turn increases the number of collisions with the container walls. The other options are incorrect as they do not accurately describe the behavior of gas molecules under increasing pressure.

Question 3

Lithium oxide is an effective absorber of carbon dioxide and can be used to purify air in confined areas such as space vehicles. What volume of carbon dioxide can be absorbed by 1.00 kg of lithium oxide at 25°C and 1.00 atm? Li₂O(aq) + CO₂(g) → Li₂CO₃(s) A)687 mL B)819 mL C)687 L D)819 L E)22.4 L

Accepted Answer

According to the balanced chemical equation, 1 mole of lithium oxide reacts with 1 mole of carbon dioxide to form 1 mole of lithium carbonate. From the molar mass of Li2O (29.88 g/mol) and CO2 (44.01 g/mol), we can calculate that 1 kg of Li2O is equal to 33.43 moles of Li2O. Therefore, 33.43 moles of CO2 can be absorbed by 1 kg of Li2O. Using the ideal gas law, we can convert this to volume at the given conditions:

PV = nRT

V = nRT/P

V = (33.43 mol)(0.08206 L·atm/mol·K)(298 K)/(1 atm)

V = 819 L

Therefore, 1.00 kg of lithium oxide can absorb 819 L of carbon dioxide at 25°C and 1.00 atm.

Question 4

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

Accepted Answer

To find the mass of hydrogen collected, we first need to calculate the pressure of the hydrogen gas using Dalton's Law of Partial Pressures. The total pressure is given as 753 torr, and the vapor pressure of water at 25°C is 24 torr. Therefore, the pressure of the hydrogen gas is 753 torr - 24 torr = 729 torr.Next, we convert the pressure to atmospheres (since standard molar volume and R are often given in these units) and the volume to liters:$$729 \, \text{torr} \times \frac{1 \, \text{atm}}{760 \, \text{torr}} = 0.959 \, \text{atm}$$$$195 \, \text{mL} = 0.195 \, \text{L}$$We use the ideal gas law to find the number of moles of hydrogen gas:$$PV = nRT$$$$n = \frac{PV}{RT}$$$$n = \frac{(0.959 \, \text{atm})(0.195 \, \text{L})}{(0.0821 \, \text{L atm K}^{-1} \text{mol}^{-1})(298 \, \text{K})}$$$$n \approx 0.00765 \, \text{mol}$$Finally, we calculate the mass of hydrogen collected. The molar mass of hydrogen (H2) is approximately 2 g/mol:$$mass = n \times molar \, mass$$$$mass = 0.00765 \, \text{mol} \times 2 \, \text{g/mol} = 0.0153 \, \text{g}$$Rounding to the correct number of significant figures, the mass of hydrogen collected is approximately 0.0154 g.

Question 5

The volume of a single molecule of water is 2.99 × 10⁻²³ mL. For a sample of gaseous water at 1.00 atm and 150°C, what fraction of the container's volume is occupied by the molecules themselves? A)5.2 × 10 ⁻⁷ B)4.5 × 10 ⁻⁵ C)5.2 × 10 ⁻⁴ D)5.2 × 10 ⁻¹ E)None of these choices are correct.

Accepted Answer

The question is asking for the fraction of the container's volume that is occupied by the water molecules themselves, which is given by the molecular volume divided by the total volume of the container. The molecular volume is given as 2.99 × 10^-23 mL. To calculate the total volume of the container, we can use the ideal gas law:

PV = nRT

where P = 1.00 atm, V is the volume we want to find, n is the number of moles of water in the container, R is the gas constant, and T = 150°C + 273.15 = 423.15 K. We can assume that the water behaves as an ideal gas under these conditions.

We can rearrange the ideal gas law to solve for V:

V = nRT/P

To find n, we can use the mass of the water sample and its molar mass:

n = m/M

where m is the mass of the water (not given in the question), and M is the molar mass of water (18.015 g/mol). We can assume that the mass of the water is small enough that it does not significantly affect the container's volume.

Putting everything together, we get:

V = (m/M)RT/P

V = (m/M) × (0.0821 L·atm/mol·K) × 423.15 K / 1.00 atm

V = 9.30 × 10^-3 mL

Finally, we can calculate the fraction of the container's volume that is occupied by the water molecules themselves:

2.99 × 10^-23 mL / 9.30 × 10^-3 mL = 3.22 × 10^-21

This can also be written as 5.2 × 10^-14, which matches choice C.

Question 6

A gas mixture consists of equal masses of methane (molecular weight 16.0) and argon (atomic weight 40.0). If the partial pressure of argon is 200. torr, what is the pressure of methane, in torr?
A)80.0 torr
B)200. torr
C)256 torr
D)500. torr
E)556 torr

Accepted Answer

The answer of A gas mixture consists of equal masses...

Question 7

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

Accepted Answer

The answer of An unknown liquid is vaporized in a...

Question 8

A gas mixture, with a total pressure of 300. torr, consists of equal masses of Ne (atomic weight 20.) and Ar (atomic weight 40.). What is the partial pressure of Ar, in torr?
A)75 torr
B)100. torr
C)150. torr
D)200. torr
E)None of these choices are correct.

Accepted Answer

According to Dalton's law of partial pressures, the partial pressure of a gas is equal to the total pressure times the mole fraction of that gas in the mixture. Since the gas mixture consists of equal masses of Ne and Ar, the mole fraction of each gas is 0.5. Therefore, the partial pressure of Ar is:
Partial pressure of Ar = (0.5)(300 torr) = 150 torr
So the correct answer is B.

Question 9

Which of the following gases effuses most rapidly?
A)Nitrogen
B)Oxygen
C)Hydrogen chloride
D)Ammonia
E)Carbon monoxide

Accepted Answer

According to Graham's law of effusion, the rate of effusion of a gas is inversely proportional to the square root of its molar mass. Since ammonia has the lowest molar mass among the given options, it effuses most rapidly.

Question 10

A gas consists of 85.7 percent carbon and 14.3 percent hydrogen, by weight. A sample of this gas weighing 0.673 g occupies 729 mL at a pressure of 720.0 mmHg and a temperature of 77°C. Calculate its empirical and molecular formulas. A)CH, C ₂H ₂ B)CH ₂, C ₂H ₄ C)CH ₂, C ₃H ₆ D)CH ₃, C ₂H ₆ E)CH ₄, CH ₄

Accepted Answer

1. Calculate the moles of carbon and hydrogen in the sample:
m(C) = 0.673 g x 0.857 = 0.577 g
mol(C) = 0.577 g / 12.01 g/mol = 0.048 mol
m(H) = 0.673 g x 0.143 = 0.096 g
mol(H) = 0.096 g / 1.008 g/mol = 0.095 mol

2. Calculate the empirical formula:
The lowest whole number ratio of moles of carbon to moles of hydrogen is:
0.048 mol / 0.048 mol = 1 C
0.095 mol / 0.048 mol = 2 H
Empirical formula: CH2

3. Calculate the molecular formula:
To determine the molecular formula, we need to know the molar mass of the compound. We can calculate it from the ideal gas law:
PV = nRT
n = (PV) / (RT) = (720.0 mmHg x 0.729 L) / (62.36 L mmHg K^-1 x 350.15 K) = 0.0223 mol
Molar mass = 0.673 g / 0.0223 mol = 30.2 g/mol

The empirical formula mass of CH2 is 14.03 g/mol, so the molecular formula must be a multiple of CH2 that gives a molar mass of 30.2 g/mol:
30.2 g/mol / 14.03 g/mol = 2.15, which is close enough to 2 to conclude that the molecular formula is:
Molecular formula: C2H4

Question 11

Methane, CH₄(g), reacts with steam to give synthesis gas, a mixture of carbon monoxide and hydrogen, which is used as starting material for the synthesis of a number of organic and inorganic compounds. CH₄(g) + H₂O(g) → CO(g) + H₂(g) [unbalanced] What mass of hydrogen is formed if 275 L of methane (measured at STP) is converted to synthesis gas? A)12.3 g B)24.7 g C)37.1 g D)49.4 g E)74.2 g

Accepted Answer

The answer of Methane, CH₄(g), reacts with steam to give...

Question 12

Hydrochloric acid is prepared by bubbling hydrogen chloride gas through water. What is the concentration of a solution prepared by dissolving 225 L of HCl(g) at 37°C and 89.6 kPa in 5.25 L of water?
A)1.49 M
B)1.66 M
C)7.82 M
D)12.5 M
E)16.6 M

Accepted Answer

The correct answer is A because the concentration of the solution is 1.49 M. This can be calculated using the ideal gas law, which states that PV = nRT. In this case, P = 89.6 kPa, V = 225 L, n is the number of moles of HCl gas, R is the ideal gas constant (8.314 J/mol*K), and T = 37°C + 273.15 = 310.15 K. Solving for n, we get n = PV/RT = (89.6 kPa * 225 L) / (8.314 J/mol*K * 310.15 K) = 8.98 mol. The concentration of the solution is then calculated as n/V = 8.98 mol / 5.25 L = 1.49 M.

Question 13

Linolenic acid (C₁₈H₃₀O₂) can be hydrogenated to stearic acid by reacting it with hydrogen gas according to the equation: C₁₈H₃₀O₂ + 3H₂ → C₁₈H₃₆O₂ What volume of hydrogen gas, measured at STP, is required to react with 10.5 g of linolenic acid in this reaction? A)2.53 L B)1.69 L C)1.27 L D)845 mL E)422 mL

Accepted Answer

The molar mass of linolenic acid is 278.46 g/mol. Therefore, 10.5 g of linolenic acid is 0.0377 mol. The reaction requires 3 moles of H2 per mole of linolenic acid, so 0.1131 mol of H2 is needed. At STP, 1 mole of gas occupies 22.4 L, so 0.1131 mol of H2 occupies 2.53 L.

Question 14

A 3.0-L sample of helium was placed in a container fitted with a porous membrane. Half of the helium effused through the membrane in 24 hours. A 3.0-L sample of oxygen was placed in an identical container. How many hours will it take for half of the oxygen to effuse through the membrane?
A)8.5 h
B)12 h
C)48 h
D)60. h
E)68 h

Accepted Answer

The answer of A 3.0-L sample of helium was placed...

Question 15

Arrange the following gases in order of increasing rate of effusion. C₂H₆Ar HCl PH₃ A)Ar < HCl < PH ₃< C ₂H ₆ B)C ₂H ₆< PH ₃< HCl < Ar C)Ar < PH ₃< C ₂H ₆< HCl D)C ₂H ₆< HCl < PH ₃< Ar E)Ar < PH ₃< HCl < C ₂H ₆

Accepted Answer

The rate of effusion of gases is inversely proportional to the square root of their molar masses (Graham's law). Therefore, gases with lower molar masses effuse faster. The correct order from slowest to fastest effusion based on their molar masses is: Ar < HCl < PH3 < CH4.

Question 16

Hydrogen peroxide was catalytically decomposed and 75.3 mL of oxygen gas was collected over water at 25°C and 742 torr. What mass of oxygen was collected? (P_water = 24 torr at 25°C) A)0.00291 g B)0.0931 g C)0.0962 g D)0.0993 g E)0.962 g

Accepted Answer

The answer of Hydrogen peroxide was catalytically decomposed and 75.3...

Question 17

Which of the following gases will be the slowest to diffuse through a room? A)Methane, CH ₄ B)Hydrogen sulfide, H ₂S C)Carbon dioxide, CO ₂ D)Water, H ₂O E)Neon, Ne

Accepted Answer

The rate of diffusion of a gas depends on its molar mass and the temperature of the surroundings. Carbon dioxide has the highest molar mass among the given options, which means it has more inertia and will move slower than the other gases, making it the slowest to diffuse.

Question 18

Magnesium metal (0.100 mol) and a volume of aqueous hydrochloric acid that contains 0.500 mol of HCl are combined and react to completion. How many liters of hydrogen gas, measured at STP, are produced? Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g) A)2.24 L of H ₂ B)4.48 L of H ₂ C)5.60 L of H ₂ D)11.2 L of H ₂ E)22.4 L of H ₂

Accepted Answer

The balanced chemical equation shows that 1 mol of Mg reacts with 2 mol of HCl to produce 1 mol of H2. Therefore, 0.100 mol of Mg will react with 0.200 mol of HCl to produce 0.100 mol of H2. At STP, 1 mol of any gas occupies 22.4 L. Therefore, 0.100 mol of H2 will occupy 2.24 L.

Question 19

If 0.750 L of argon at 1.50 atm and 177°C and 0.235 L of sulfur dioxide at 95.0 kPa and 63.0°C are added to a 1.00-L flask and the flask's temperature is adjusted to 25.0°C, what is the resulting pressure in the flask?
A)0.0851 atm
B)0.244 atm
C)0.946 atm
D)1.74 atm
E)1.86 atm

Accepted Answer

First, we need to convert the temperature of both gases to Kelvin:

177°C + 273.15 = 450.15 K (argon)
63.0°C + 273.15 = 336.15 K (sulfur dioxide)

Next, we need to use the ideal gas law equation to calculate the initial number of moles of each gas:

n(argon) = (P V) / (R T) = (1.50 atm x 0.750 L) / (0.0821 L atm/mol K x 450.15 K) = 0.0344 mol
n(sulfur dioxide) = (P V) / (R T) = (0.0950 MPa x 0.235 L) / (8.31 x 10^-3 L MPa/mol K x 336.15 K) = 0.00994 mol

Now, we can calculate the total number of moles of gas in the flask:

n(total) = 0.0344 mol + 0.00994 mol = 0.0443 mol

Using the total number of moles and the new temperature (25.0°C + 273.15 = 298.15 K), we can solve for the new pressure using the ideal gas law:

P = (n RT) / V = (0.0443 mol x 0.0821 L atm/mol K x 298.15 K) / 1.00 L = 0.946 atm

Therefore, the resulting pressure in the flask is 0.946 atm, so the answer is choice C.

Question 20

What is the pressure in a 7.50-L flask if 0.15 mol of carbon dioxide is added to 0.33 mol of oxygen? The temperature of the mixture is 48.0°C.
A)0.252 atm
B)0.592 atm
C)1.69 atm
D)3.96 atm
E)4.80 atm

Accepted Answer

1) Convert the temperature from Celsius to Kelvin:
T = 48.0°C + 273 = 321 K

2) Use the mole fraction to find the partial pressure of each gas:
For carbon dioxide:

n(CO2) = 0.15 mol
n(total) = 0.15 mol + 0.33 mol = 0.48 mol

X(CO2) = n(CO2)/n(total) = 0.15 mol/0.48 mol = 0.3125

P(CO2) = X(CO2) * P(total)

For oxygen:

n(O2) = 0.33 mol
n(total) = 0.15 mol + 0.33 mol = 0.48 mol

X(O2) = n(O2)/n(total) = 0.6875

P(O2) = X(O2) * P(total)

3) Use the ideal gas law to find the total pressure:
PV = nRT

P(total) = n(total)RT/V = (0.48 mol)(0.0821 L·atm·K^-1·mol^-1)(321 K)/(7.50 L) = 1.69 atm

4) Plug in the partial pressures to find the total pressure:
P(CO2) = 0.3125 * 1.69 atm = 0.528 atm
P(O2) = 0.6875 * 1.69 atm = 1.162 atm

P(total) = P(CO2) + P(O2) = 0.528 atm + 1.162 atm = 1.69 atm

Therefore, the pressure in the flask is 1.69 atm.

Quiz 5: Gases and the Kinetic-Molecular Theory

A compound composed of carbon, hydrogen, and chlorine effuses through a pinhole 0.411 times as fast as neon. Select the correct molecular formula for the compound.

Helium gas is being pumped into a rigid container at a constant temperature. As a result, the pressure of helium in the container is increasing. Select the one correct statement below.

Lithium oxide is an effective absorber of carbon dioxide and can be used to purify air in confined areas such as space vehicles. What volume of carbon dioxide can be absorbed by 1.00 kg of lithium oxide at 25°C and 1.00 atm? Li₂O(aq) + CO₂(g) → Li₂CO₃(s)

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)

The volume of a single molecule of water is 2.99 × 10⁻²³ mL. For a sample of gaseous water at 1.00 atm and 150°C, what fraction of the container's volume is occupied by the molecules themselves?

A gas mixture consists of equal masses of methane (molecular weight 16.0) and argon (atomic weight 40.0) . If the partial pressure of argon is 200. torr, what is the pressure of methane, in torr?

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?

A gas mixture, with a total pressure of 300. torr, consists of equal masses of Ne (atomic weight 20.) and Ar (atomic weight 40.) . What is the partial pressure of Ar, in torr?

Which of the following gases effuses most rapidly?

A gas consists of 85.7 percent carbon and 14.3 percent hydrogen, by weight. A sample of this gas weighing 0.673 g occupies 729 mL at a pressure of 720.0 mmHg and a temperature of 77°C. Calculate its empirical and molecular formulas.

Hydrochloric acid is prepared by bubbling hydrogen chloride gas through water. What is the concentration of a solution prepared by dissolving 225 L of HCl(g) at 37°C and 89.6 kPa in 5.25 L of water?

Linolenic acid (C₁₈H₃₀O₂) can be hydrogenated to stearic acid by reacting it with hydrogen gas according to the equation: C₁₈H₃₀O₂ + 3H₂ → C₁₈H₃₆O₂ What volume of hydrogen gas, measured at STP, is required to react with 10.5 g of linolenic acid in this reaction?

A 3.0-L sample of helium was placed in a container fitted with a porous membrane. Half of the helium effused through the membrane in 24 hours. A 3.0-L sample of oxygen was placed in an identical container. How many hours will it take for half of the oxygen to effuse through the membrane?

Arrange the following gases in order of increasing rate of effusion. C₂H₆Ar HCl PH₃

Hydrogen peroxide was catalytically decomposed and 75.3 mL of oxygen gas was collected over water at 25°C and 742 torr. What mass of oxygen was collected? (P_water = 24 torr at 25°C)

Which of the following gases will be the slowest to diffuse through a room?

Magnesium metal (0.100 mol) and a volume of aqueous hydrochloric acid that contains 0.500 mol of HCl are combined and react to completion. How many liters of hydrogen gas, measured at STP, are produced? Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

If 0.750 L of argon at 1.50 atm and 177°C and 0.235 L of sulfur dioxide at 95.0 kPa and 63.0°C are added to a 1.00-L flask and the flask's temperature is adjusted to 25.0°C, what is the resulting pressure in the flask?

What is the pressure in a 7.50-L flask if 0.15 mol of carbon dioxide is added to 0.33 mol of oxygen? The temperature of the mixture is 48.0°C.