According to the kinetic theory of gases, the pressure exerted by a gas is due to

Analysis of the Question

The question asks for the fundamental cause of gas pressure based on the Kinetic Molecular Theory (KMT). To answer this, we must look at how gas particles behave according to the assumptions of this theory.

Concept Explanation

The Kinetic Molecular Theory describes gases as being composed of a large number of tiny particles (atoms or molecules) that are in constant, random, and rapid motion.

Key principles of the KMT regarding pressure include:

1. Constant Motion: Gas particles move in straight lines until they collide with each other or the walls of their container.
2. Elastic Collisions: When these particles hit the walls of the container, they exert a force.
3. Definition of Pressure: In physics and chemistry, pressure is defined as Force per unit area ($P = F/A$).
4. The Source of Force: Since the particles are constantly bombarding the inner surfaces of the container, the cumulative force of these millions of tiny collisions per second creates what we measure as gas pressure.

Step-by-Step Solution

• Evaluate Option A: Gas particles move translationally (they move from place to place); they do not just vibrate in a fixed position like particles in a solid.
• Evaluate Option B: The weight of gas particles is negligible and does not contribute to the pressure exerted on the walls of a container.
• Evaluate Option C: A fundamental assumption of the Kinetic Theory for an ideal gas is that there are no significant attractive or repulsive forces between gas particles.
• Evaluate Option D: As established by the KMT, pressure is the result of the continuous bombardment (collisions) of gas particles against the walls of the container. Each collision exerts a tiny force, and the sum of these forces over the area of the container wall results in pressure.

Conclusion

Exam Tip

Whenever you see a question about the "Kinetic Theory of Gases," remember the acronym "R-E-C":

• Random motion.
• Elastic collisions (no energy is lost).
• Collisions with walls create pressure.