Final answer:
Momentum is directly proportional to the pressure in a gas; this relationship is explained by the Kinetic-Molecular Theory, which accounts for the number of molecular impacts against container walls and the momentum of the gas molecules (b).
Step-by-step explanation:
Momentum is closely related to the pressure exerted by a gas. On the molecular level, the pressure of a gas is a result of the cumulative impacts of its molecules against the walls of a container. When gas molecules collide with the walls, they exert a force over a certain area. The momentum of each molecule changes upon impact, and this change in momentum over time is what we observe as pressure.
The relationship between momentum and pressure is conceptualized by the Kinetic-Molecular Theory (KMT), which explains that gas pressure directly depends on the number of molecules hitting a unit area of the wall per unit of time and also the average momentum of those molecules. Since momentum is mass times velocity, at a given mass, the velocity of particles (which ties into the temperature of gas) dictates their momentum, and consequently, the pressure they generate upon colliding with the container walls.
So, while momentum itself is not synonymous with pressure, it is directly related to it. Higher momentum of gas particles (meaning either more mass or higher velocity) will result in greater pressure, assuming the container's volume and the number of gas molecules remain constant. Therefore, the correct answer to how momentum is related to the pressure exerted by a gas is (b) Momentum is directly proportional to pressure in the context of their interactions within a gas.