Question

the closeness of particles of gas and their low speeds allow intermolecular forces to become important at certain pressures and temperatures. which best describes this statement?

• this is a postulate of the kinetic-molecular theory.
• this is a limitation of the kinetic-molecular theory.
• this describes ideal gas behavior without the kinetic-molecular theory.
• this describes ideal gas behavior using the kinetic-molecular theory.

Explanation:

Analyze the given statement

The statement is: "The closeness of particles of gas and their low speeds allow intermolecular forces to become important at certain pressures and temperatures."
This statement describes conditions (high pressure, low temperature) where gas particles are close together and moving slowly, causing intermolecular attractions to significantly influence their behavior.

Recall Kinetic Molecular Theory postulates

Using the Kinetic Molecular Theory knowledge point, we recall its core postulates for an ideal gas:

1. Gas particles are in constant, random motion.
2. The volume of individual gas particles is negligible compared to the container volume.
3. There are no attractive or repulsive forces (intermolecular forces) between gas particles.
4. Collisions between particles are perfectly elastic.

Identify the limitation of the theory

Using the Real Gas Deviations knowledge point, we analyze how real gases deviate from ideal behavior.
The Kinetic Molecular Theory assumes that intermolecular forces are completely negligible. However, in reality, when a gas is subjected to high pressure (particles are close together) and low temperature (particles move slowly), intermolecular forces do become significant. Therefore, the statement describes a scenario where the assumptions of the Kinetic Molecular Theory fail, representing a clear limitation of the theory when describing real gases.

Evaluate the given options

• Option 1: "This is a postulate of the kinetic-molecular theory" — Incorrect, because the theory assumes intermolecular forces are negligible.
• Option 2: "This is a limitation of the kinetic-molecular theory" — Correct, as it highlights where the theory's assumptions about negligible intermolecular forces break down.
• Option 3: "This describes ideal gas behavior without the kinetic-molecular theory" — Incorrect, ideal gases do not have significant intermolecular forces.
• Option 4: "This describes ideal gas behavior using the kinetic-molecular theory" — Incorrect, for the same reason.

Answer:

• This is a postulate of the kinetic-molecular theory
• This is a limitation of the kinetic-molecular theory (Correct answer)
• This describes ideal gas behavior without the kinetic-molecular theory
• This describes ideal gas behavior using the kinetic-molecular theory