Pressure is the result of elastic collision of molecules with the container's wall.
Molecules are separated by great distances compared to their sizes.
All the molecules move in straight line between collision and with same velocity.
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The Correct Option isD
Solution and Explanation
The question concerns the assumptions made in the kinetic theory of gases. The kinetic theory makes several assumptions to explain the behavior of gases. Let's analyze each option to identify the incorrect one:
Momentum and energy always remain conserved.
This assumption is true. According to the kinetic theory of gases, during the elastic collisions between gas molecules themselves or with the walls of the container, the total momentum and energy are conserved.
Pressure is the result of elastic collision of molecules with the container's wall.
This is a correct assumption. The pressure exerted by gas is due to the continuous and elastic collisions between the gas molecules and the walls of the container.
Molecules are separated by great distances compared to their sizes.
This statement is accurate. In a gas, the average distance between molecules is indeed much larger than the size of the molecules themselves, which is why gases are easily compressible.
All the molecules move in straight line between collision and with same velocity.
This is the incorrect assumption. While gas molecules do move in a straight line between collisions, the claim that they all move with the same velocity is incorrect. In reality, gas molecules move with a variety of speeds, described by the Maxwell-Boltzmann distribution. Over time, the velocity distribution in a gas is determined by factors like temperature.
Based on the analysis above, the assumption "All the molecules move in straight line between collision and with same velocity" is incorrect because gas molecules do not all have the same velocity; their velocities vary, which is a fundamental aspect of the kinetic theory.
