Question

You found that the average spacing of atoms/molecules in a gas at STP is about 10 particle diameters (~10 ). You also know that the molecules of an ideal gas do not interact. Relate these two ideas, The average distance between gas molecules at STP, and The non-interaction between molecules of an ideal gas, to the particle-particle interaction model as represented by the PE graph.

Answer 1

Following is the potential energy curve:

The force of interaction at any point of separation between two molecules is given by the negative of the slope of the tangent to the curve at that point.

F = -dU/dx

As we can see, the slope is zero at distances greater than 2 particle diameters. It is only when the distance reduces to very small levels that the interactive forces come into play, because then the nuclei start exerting repulsive forces on each other.

So, at the average distances of 10 particle diameters, the force is essentially zero.

Hope this helps !