Gas Intro

A gaseous air‑fuel mixture in a sealed car engine cylinder has an initial volume of 600. mL at 1.0 atm. To prepare for ignition of the fuel, a piston moves within the cylinder, reducing the volume of the air‑fuel mixture to 50. mL at constant temperature. Assuming ideal behavior, what is the new pressure of the air‑fuel mixture?

• About 0.083 atm, because the initial volume of the gas mixture was 12 times larger than its final volume.

• About 12 atm, because the volume of the gas mixture decreased by a factor of 12.

• About 120. atm, because the initial volume of the gas mixture was 120 times larger than its final volume.

• About 550. atm, because the change in the volume of the gas mixture was 550. mL.

At 10.°C, 20.g of oxygen gas exerts a pressure of 2.1atm in a rigid, 7.0L cylinder. Assuming ideal behavior, if the temperature of the gas was raised to 40.°C, which statement indicates the new pressure and explains why?

• 1.9 atm, because the pressure P decreases by the proportion 283/313

• 2.3 atm, because the pressure P increases by the proportion 313/283

• 0.52 atm, because the pressure P decreases by the proportion 10/40

• 8.4 atm, because the pressure P increases by the proportion 40/10

Tags

NGSS.HS-PS3-4

Two sealed, rigid 5.0L containers each contain a gas at the same temperature but at a different pressure, as shown above. Also shown are the results of transferring the entire contents of container 1 to container 2. No gases escape during the transfer. Assuming ideal behavior, which statement is correct regarding the total pressure of the gases after they are combined?

• The total pressure of the gases in the mixture is the sum of the initial pressures of oxygen gas and nitrogen gas because pressure only depends on the total amount of gas when volume and temperature are held constant.

• The total pressure of the gases in the mixture is lower than the sum of the initial pressures of oxygen and nitrogen because some of the energy of the particles will be lost due to an increase in the number of collisions.

• The total pressure of the gases in the mixture is higher than the sum of the initial pressures of oxygen and nitrogen because of the intermolecular forces that develop between oxygen and nitrogen molecules.

• The total pressure of the gases in the mixture cannot be determined because the actual value of the temperature is not given.

The diagrams above use arrows to represent the speed of a gas particle. Which of the diagrams best represents the speed of the particles of a gas at a fixed temperature, and why?

• Diagram 1, because all the particles have the same speed.

• Diagram 1, because the particles are moving in different directions.

• Diagram 2, because the particles have a net kinetic energy of zero.

• Diagram 2, because the particles have a variety of different speeds.

Tags

NGSS.HS-PS3-4

Let P and V represent the pressure and volume of the Xe(g) in the container. If a piston is used to reduce the volume of the gas to V/2 at a constant temperature, what is the new pressure in the container in terms of the original pressure, P ?

• P/2

• PV/2

• 2PV

• 2P

What happens to the average speed of the Xe atoms in the container as the original volume V is reduced to V/2 at a constant temperature?

• Average speed stays the same because temperature is constant

• Average speed increases because volume is reduced

• Average speed decreases because volume is reduced

A 2 L sample of N2(g) and a 1 L sample of Ar(g), each originally at 1 atm and 0°C, are combined in

a 1 L tank. If the temperature is held constant, what is the total pressure of the gases in the tank?

• 1

• 2

• 3

• 4

A balloon filled with 0.25 mol of He(g) at 273 K and 1 atm is allowed to rise through the atmosphere. Which of the following explains what happens to the volume of the balloon as it rises from ground level to an altitude where the air temperature is 220 K and the air pressure is 0.1 atm?

• The volume will increase because the decrease in air pressure will have a greater effect than the decrease in temperature.

• The volume will remain unchanged because of the counteracting effects of the decrease in temperature and the decrease in air pressure.

• The volume will decrease because the decrease in temperature will have a greater effect than the decrease in air pressure

• It cannot be determined whether the volume of the balloon will increase, decrease, or remain the same without knowing the initial volume of the balloon.

A flask contains 0.25 mole of SO₂(g), 0.50 mole of CH₄(g), and 0.50 mole of O₂(g). The total pressure of the gases in the flask is 800 mm Hg. What is the partial pressure of the SO₂(g) in the flask?

• 800 mm Hg

• 600 mm Hg

• 200 mm Hg

• 250 mm Hg

• 160 mm Hg

A 0.5 mol sample of He(g) and a 0.5 mol sample of Ne(g) are placed separately in two 10.0 L rigid containers at 25°C. Each container has a pinhole opening. Which of the gases, He(g) or Ne(g), will escape faster through the pinhole and why?

• He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.

• Ne(g) will escape faster because its initial pressure in the container is higher.

• Ne(g) will escape faster because the Ne(g) atoms have a higher average kinetic energy than the He(g) atoms.

• Both gases will escape at the same rate because the atoms of both gases have the same average kinetic energy.

Tags

NGSS.HS-PS2-1