Gas Properties

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.

The reaction between NO(g) and O₂(g) to produce NO₂(g) in a rigid reaction vessel is represented in the diagram above. The pressure inside the container is recorded using a pressure gauge. Which of the following statements correctly predicts the change in pressure as the reaction goes to completion at constant temperature, and provides the correct explanation?

• The pressure will increase because the product molecules have a greater mass than either of the reactant molecules.

• The pressure will decrease because there are fewer molecules of product than reactants.

• The pressure will decrease because the product molecules have a lower average speed than the reactant molecules.

• The pressure will not change because the total mass of the product molecules is the same as the total mass of the reactant molecules.

Tags

NGSS.HS-PS1-7

The density of the gas, in g/L, is

• greatest in container A

• greatest in container B

• greatest in container C

• the same in all three containers

Tags

NGSS.HS-PS3-4

Equimolar samples of CH₃OH(l) and C₂H₅OH(l) are placed in separate, previously evacuated, rigid 2.0 L vessels. Each vessel is attached to a pressure gauge, and the temperatures are kept at 300 K. In both vessels, liquid is observed to remain present at the bottom of the container at all times.

The temperature of the CH₃OH is increased from 300 K to 400 K to vaporize all the liquid, which increases the pressure in the vessel to 0.30 atm. The experiment is repeated under identical conditions but this time using half the mass of CH₃OH that was used originally. What will be the pressure in the vessel at 400 K?

• 0.15 atm

• 0.30 atm

• 0.40 atm

• 0.60 atm

Tags

NGSS.HS-PS3-4

If the volume of a confined gas is doubled while the temperature remains constant, what change (if any) would be observed in the pressure?

• It would be half as large.

• It would double.

• It would be four times as large.

• It would remain the same.

A given mass of a gas in a rigid container is heated from 100°C to 500°C. Which of the following responses best describes what will happen to the pressure of the gas? The pressure will

• decrease by a factor of five.

• increase by a factor of five.

• increase by a factor of about two.

• increase by a factor of about eight.

What is the density of CH₄ at 200°C and 0.115 atm?

• 0.0475 g/L

• 0.0716 g/L

• 0.542 g/L

• 0.870 g/L

What is the molar mass of a gas which has a density of 1.30 g/L measured at 27°C and 0.400 atm?

• 38.0 g/mol

• 48.0 g/mol

• 61.5 g/mol

• 80.0 g/mol

A 4.50 L flask of Ar at 23°C and 734 torr is heated to 55°C. What is the new pressure?

• 366 atm

• 935 torr

• 1.25 torr

• 1.07 atm

At what temperature will 41.6 grams N₂ exert a pressure of 815 torr in a 20.0 L cylinder?

• 134 K

• 176 K

• 238 K

• 337 K