Final answer:
The average force per molecule-wall collision will decrease by a factor of 2 when the volume is doubled from 16.3 L to 32.7 L while maintaining constant temperature, as the pressure is inversely proportional to volume for a given amount of gas at constant temperature.
Step-by-step explanation:
When examining the effects of changing the volume of a gas while holding temperature constant on the average force per molecule-wall collision, we use our understanding of the kinetic theory of gases. According to this theory, if we increase the volume of a container and keep the temperature the same, the pressure decreases as a result of the molecules having more space in which to move and therefore will collide with the container walls less frequently.
Since the pressure is proportional to the number of collisions per unit area, when the volume is doubled from 16.3 L to 32.7 L at constant temperature, the number of collisions per unit area will be halved. This implies that the pressure is halved, and since force is proportional to pressure, the average force per molecule-wall collision decreases by the same factor. So, in this scenario, the average force per molecule-wall collision decreases by a factor of 2, which corresponds to option (b).