Question 1

Four containers, each with the same volume and at the same temperature, are shown in the following diagrams. Which container is at the highest pressure?

Accepted Answer

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Question 2

Which of the following graphs shows the correct relationship between the pressure and temperature of an ideal gas in a given volume? Note the origin corresponds to P = 0 atm and T = 0 K.

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Question 3

A 22.4-L sealed chamber at 273 K is filled with air at a pressure of 1.00 atm. A solid state chemical reaction in the chamber adds 1.25 mol hydrogen gas. The temperature of the chamber must be decreased to ________ to maintain the pressure at 1.00 atm.

Accepted Answer

The initial conditions are a volume of 22.4 L, a temperature of 273 K, and a pressure of 1.00 atm. The addition of 1.25 mol of hydrogen gas increases the amount of gas in the chamber. To maintain the pressure at 1.00 atm while the amount of gas increases, the temperature must decrease. Using the ideal gas law (PV=nRT) and assuming the volume and pressure remain constant, the temperature must decrease proportionally to the increase in the amount of gas. Initially, the chamber contains 1 mol of gas (since 22.4 L at 273 K and 1 atm is the molar volume of an ideal gas). Adding 1.25 mol of hydrogen increases the total moles of gas to 2.25 mol. To maintain the same pressure, the temperature must decrease in the same ratio as the initial conditions to the final conditions, which is 273 K * (1 mol / 2.25 mol) = 121 K.

Question 4

What volume is occupied by 1.00 mol of an ideal gas at 1.00 atm and 0.00°C?

Accepted Answer

According to the Avogadro's Law, one mole of any gas occupies 22.4 L at standard temperature and pressure (STP), which is defined as 1 atm of pressure and 0°C. The given conditions for the gas (1.00 atm and 0.00°C) are exactly the same as STP, so the volume will also be 22.4 L (approximately). Therefore, the correct answer is choice A.

Question 5

An unknown gas held in a 25.0 mL flask at 45°F exerts a pressure of 25 mTorr. Using this information with the ideal gas law, it is possible to determine ________

Accepted Answer

Using the ideal gas law, you can calculate the number of moles of the gas, which can then be converted to the number of molecules using Avogadro's number.

Question 6

Which of the following graphs shows the correct relationship between the temperature and volume of an ideal gas at a given pressure? Note the origin corresponds to V = 0 and T = 0.

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Question 7

A balloon vendor at a street fair is using a tank of helium to inflate the balloons. The tank has a volume of 75 L and a pressure of 95 atm at 22°C. The valve is not closed completely and some helium leaks out. After some time, the pressure drops to 85 atm. How many moles of helium have been lost?

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Question 8

A sample of gas at 4.0 atm and 25.0 mL is heated from 25°C to 40°C. If the pressure remains constant, what is the final volume of the gas?

Accepted Answer

According to Charles's Law, which states that volume is directly proportional to temperature (in Kelvin) at constant pressure, the final volume can be calculated using the formula V1/T1 = V2/T2. Converting temperatures to Kelvin and solving for V2 gives approximately 26.2 mL.

Question 9

What is the volume of a gas that exerts a pressure of 457 mm Hg if it exerted a pressure of 2.50 atm when its volume was 25.0 mL?

Accepted Answer

We can use the Boyle's Law formula to solve for the new volume:

(P1)(V1) = (P2)(V2)

where P1 = 2.50 atm, V1 = 25.0 mL, P2 = 457 mmHg, and we want to solve for V2.

First, we need to convert the pressure in mmHg to atm:

457 mmHg x (1 atm/760 mmHg) = 0.601 atm

Now we can plug in the values:

(2.50 atm)(25.0 mL) = (0.601 atm)(V2)

V2 = (2.50 atm)(25.0 mL)/(0.601 atm) = 104 mL = 0.104 L

Therefore, the answer is C.

Question 10

A balloon is filled with 3.00 L of helium at a pressure of 765 torr. What is the volume of the balloon at an altitude where the pressure in the balloon is 530 torr?

Accepted Answer

The volume of the balloon at the new pressure can be found using Boyle's Law, which states that P1V1 = P2V2, where P1 and V1 are the initial pressure and volume, and P2 and V2 are the final pressure and volume. Rearranging for V2 gives V2 = (P1V1)/P2. Substituting the given values: V2 = (765 torr * 3.00 L) / 530 torr = 4.33 L.

Question 11

How many moles of propane are contained in a 5.00 L tank at 450 torr and 25°C?

Accepted Answer

To find the number of moles of propane, use the ideal gas law: PV = nRT. Convert pressure to atm (450 torr = 0.592 atm) and temperature to Kelvin (25°C = 298 K). Using R = 0.0821 L·atm/mol·K, solve for n: n = PV/RT = (0.592 atm)(5.00 L) / (0.0821 L·atm/mol·K)(298 K) ≈ 0.12 mol.

Question 12

Which of the following is unimportant when using the ideal gas law?

Accepted Answer

The ideal gas law, PV=nRT, applies to all gases, regardless of their chemical identity. Therefore, the chemical identity of the gas sample is unimportant when using the ideal gas law.

Question 13

In an experiment, 7.5 mol of a gas are held in a 3.5 L container at 39°C. What pressure does the gas exert if it is assumed to be ideal?

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Question 14

A gas, initially at 1.00 atm and 5.00 L, is compressed to a pressure of 15.00 atm. What is the volume of the gas at this pressure?

Accepted Answer

This problem can be solved using Boyle's Law, which states that the pressure and volume of a gas are inversely proportional when the temperature and amount of gas stay constant. Mathematically, this can be written as P1V1 = P2V2. We can plug in the values given in the problem to solve for V2:

(1.00 atm)(5.00 L) = (15.00 atm)V2

V2 = 0.333 L = 333 mL

Therefore, the answer is B) 333 mL.

Question 15

What is the pressure of a 3.5 mmol sample of ethane (C₂H₆) gas contained in a 0.500 L flask at 298 K?

Accepted Answer

We can use the ideal gas law to solve for pressure:
PV = nRT
P = nRT/V
where P is pressure in atm, n is the number of moles, R is the gas constant (0.082 L·atm/mol·K), T is the temperature in kelvin, and V is the volume in liters.
First, we need to convert the number of moles from mmol to mol:
3.5 mmol = 3.5 × 10^−3 mol
Next, we can plug in the values and convert the pressure to mm Hg:
P = (3.5 × 10^−3 mol)(0.082 L·atm/mol·K)(298 K)/(0.500 L) = 0.130 atm
P = 0.130 atm × 760 mm Hg/atm = 98.8 mm Hg ≈ 130 mm Hg

Therefore, the answer is C.

Question 16

Which statement A-D regarding an ideal gas is not correct?

Accepted Answer

Statements A through D accurately describe characteristics of an ideal gas. In an ideal gas, the volume of individual molecules is considered negligible, interactions are limited to elastic collisions, molecules move randomly, and 1 mol of an ideal gas occupies 22.4 L at standard temperature and pressure (STP).

Question 17

A 1.50 mol sample of He occupies a volume of 2.50 L at a pressure of 14.7 atm. What will be the pressure of a 1.50 mol sample of H₂ gas under the same conditions?

Accepted Answer

The pressure of a gas is independent of its chemical identity and depends only on its volume, temperature, and amount (moles) according to the ideal gas law. Since the conditions and the amount of gas are the same, the pressure will also be the same, regardless of the gas type.

Question 18

What volume is occupied by 1.00 mol of an ideal gas at 1.00 bar and 0.00°C?

Accepted Answer

At 0.00°C (273.15 K) and 1.00 bar, the volume occupied by 1.00 mol of an ideal gas is approximately 22.7 L, according to the ideal gas law and the conditions specified.

Question 19

A 25.0 L balloon is filled with 2.75 mol of helium. If the helium leaks out at the rate of 0.105 mol/hr, what is the volume of the balloon after 12.0 hr? Assume the pressure and temperature don't change.

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Question 20

Which of the gases shown here will exert the lowest pressure, assuming that each container has the same volume and temperature?

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Quiz 6: Properties of Gases: the Air We Breathe