AP Chemistry : Deviations from Ideal Gas Law

Study concepts, example questions & explanations for AP Chemistry

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Deviations From Ideal Gas Law

Under which conditions would you expect Ar to deviate the most from ideal behavior?

Possible Answers:

Ar always behaves ideally

300K and 5 atm

200 K and 10 atm

300K and 10 atm

200 K and 1 atm

Correct answer:

200 K and 10 atm

Explanation:

The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container.  At 200K (lowest temperature in the list, and the highest pressure).  This gives Ar the most time to interact due to molecular speeds and the high pressure implies the molecular size is not insignificant relative to the container.

Example Question #2 : Deviations From Ideal Gas Law

Would you expect a polar or non polar gas to deviate most from ideal gas behavior?

Possible Answers:

Polar gases, because of high dipole-dipole interactions

Non polar gases, because of high dispersion interactions

Non polar gases because of reduced overall intermolecular forces

Both polar and non polar gases behave ideally

Polar gases because of hydrogen bonding

Correct answer:

Polar gases, because of high dipole-dipole interactions

Explanation:

Polar gases would have increased interactions due to their dipoles that would lead to deviations from ideal gas behavior.

Example Question #3 : Deviations From Ideal Gas Law

Which of the following would behave most like an ideal gas?

Possible Answers:

 in 10 L

All are ideal gases because they are non-polar

 in 10 L

 in 10 L

 in 10 L

Correct answer:

 in 10 L

Explanation:

 is the smallest molecule in the list, and therefore the least size effects.

Example Question #101 : Solutions And States Of Matter

Why do gases deviate from ideal behavior as the temperature is decreased?

Possible Answers:

As the temperature is decreased the molecules have less kinetic energy and can’t maintain the intermolecular forces necessary for ideal gas behavior.

As the temperatures is decreased the molecules become frozen in place.

As the temperature is decreased the molecules have less kinetic energy and can’t break the intermolecular interactions between them.

As the temperature is decreased the molecules have more kinetic energy and break the intermolecular interactions keeping them together.

None of the above.

Correct answer:

As the temperature is decreased the molecules have less kinetic energy and can’t break the intermolecular interactions between them.

Explanation:

The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container.  As the temperature is decreased the gas molecules are moving slower and allow for a greater degree of interaction.

Example Question #5 : Deviations From Ideal Gas Law

When does a gas behave most like an ideal gas?

Possible Answers:

At high temperatures, high volume, low intermolecular interactions

At low temperatures, high volume, and low intermolecular interactions

At high temperature, high volumes, and high intermolecular interactions

At low temperatures, low volume, low intermolecular interactions

At low volumes, high temperatures, and high intermolecular interactions

Correct answer:

At high temperatures, high volume, low intermolecular interactions

Explanation:

The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container.  At high temperatures the gas molecules are moving fast enough to shorten the time scale for any interactions.  At high volumes, the molecular size becomes small relative to the size of the container, and the low interactions mean the molecules act more independently.

Learning Tools by Varsity Tutors