Q.39 Kinetic theory of an ideal gas is based upon the following assumption(s):
(A) Gases are made of molecules with negligible volume
(B) The gaseous molecules do not possess kinetic energy
(C) The molecules are in constant random motion
(D) Intermolecular forces of attraction are negligible

Kinetic theory of ideal gas assumptions forms the foundation for understanding gas behavior in physics and chemistry exams like CSIR NET. The correct options are (A), (C), and (D), as they align with core postulates explaining pressure, temperature, and volume relationships.​

Option Analysis

• (A) Gases are made of molecules with negligible volume: Correct. Kinetic theory assumes gas molecules occupy negligible volume compared to the container, allowing the ideal gas law $PV=nRT$ to hold accurately.​

• (B) The gaseous molecules do not possess kinetic energy: Incorrect. Molecules possess kinetic energy proportional to absolute temperature, driving random motion and pressure via wall collisions.​​

• (C) The molecules are in constant random motion: Correct. Molecules move randomly in all directions, leading to elastic collisions that maintain uniform kinetic energy distribution.​

• (D) Intermolecular forces of attraction are negligible: Correct. No attractive or repulsive forces exist between molecules except during brief elastic collisions, simplifying gas behavior.​

The kinetic theory of ideal gas assumptions provides a microscopic model explaining macroscopic properties like pressure and temperature. These postulates idealize gases to derive the equation $PV=nRT$, crucial for competitive exams.​

Core Assumptions

Kinetic theory rests on five main postulates:

• Gas consists of tiny molecules in constant, random motion.​

• Molecular volume is negligible relative to container volume.​

• No intermolecular forces act between molecules.​

• Collisions are perfectly elastic, conserving kinetic energy.​​

• Average kinetic energy depends only on temperature: KEavg=3/2kT.

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