# Kinetic model of an ideal gas

## Homework Statement

In the kinetic model of an ideal gas, it is assumed that:
A. The forces between the gas and the container are zero
B. The intermolecular potential energy of the molecules of the gas is constant.
C. The kinetic energy of a given gas molecule is constant
D. The momentum of a given molecule of the gas is constant

## The Attempt at a Solution

I chose D, because collisions of ideal gases are perfectly elastic, but the answer was B. I wanted to know whether this answer means that for real gases, the intermolecular potential energy is not constant. [/B]

## Answers and Replies

Andrew Mason
Science Advisor
Homework Helper
B is correct. Intermolecular potential energy is 0 for an ideal gas. The kinetic model for an ideal gas assumes that the molecules are point masses and that there are no intermolecular forces. If there were intermolecular forces one would have to take into account potential energy (as a function of intermolecular distances). For real gases there may or may not be intermolecular forces. For example, there are significant intermolecular forces between H2O molecules but not for He.

AM

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D is not correct because molecules are constantly colliding and changing direction. Momentum is a vector quantity