8.4 Review Quiz

The volume of a sample of air in a cylinder with a movable piston is 2.0 L at a pressure P₁, as shown in the diagram above. The volume is increased to 5.0 L as the temperature is held constant. The pressure of the air in the cylinder is now P₂. What effect do the volume and pressure changes have on the average kinetic energy of the molecules in the sample?

• the average kinetic energy increase

• the average kinetic energy decreased

• the average kinetic energy stays the same

• It cannot be determined how the kinetic energy is affected without knowing P₁and P₂.

A vessel contains Ar(g) at a high pressure. Which of the following statements best helps to explain why the measured pressure is significantly greater than the pressure calculated using the ideal gas law?

• The molar mass of Ar is relatively large.

• A significant number of Ar₂ molecules form.

• The attractive forces among Ar atoms cause them to collide with the walls of the container with less force.

• The combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container.

The ideal gas law best describes the properties of which of the following gases at 0^oC and 1 atm?

• PH₃

• HBr

• SO₂

• N₂

A 1.0 L sample of a pure gas is found to have a lower pressure than that predicted by the ideal gas law. The best explanation for the observation is that the molecules of the gas

• have a combined volume that is too large to be considered negligible when compared to the volume of the container

• have a low molecular mass and therefore do not strike the container walls with as much force as expected

• are attracted to each other and do not exert as much force on the container walls as they would if they had no mutual attractions

• are attracted to the sides of the container and strike the container walls with more force than expected

Non-ideal behavior for a gas is most likely to be observed under conditions of

• low temperature and high pressure.

• low temperature and low pressure.

• high temperature and high pressure.

• high temperature and low pressure.

Which of the following gases effuses at the highest rate?

• N₂

• O₂

• F₂

• Ne

Carbon dioxide gas diffuses through a porous barrier at a rate of 0.20 mL/minute. If an unknown gas diffuses through the same barrier at a rate of 0.25 mL/minute, what is the molar mass of the unknown gas?

• 28 g/mol

• 35 g/mol

• 39 g/mol

• 68 g/mol

Which of the following statements is true?

• All particles moving with the same velocity have the same kinetic energy.

• All particles at the same temperature have the same kinetic energy.

• All particles having the same kinetic energy have the same mass.

• As the velocity of a particle is doubled, the kinetic energy decreases by a factor of four.

At a given temperature, gaseous ammonia molecules (NH₃) have a velocity that is ____ gaseous sulfur dioxide molecules (SO₂).

• greater than

• less than

• equal to

• more information needed

CH₄ gas and O₂ gas are together in a container. Which statement correctly describes the velocitiesof the two molecules.

• The two molecules have the same average velocity.

• The CH₄ is moving twice as fast as the O₂.

• The CH₄ is moving faster, but not twice as fast as the O₂.

• The O₂ is moving faster than the CH₄.