Which of the following laws states that pressure and temperature are directly related at a constant volume?

The law that states that pressure and temperature are directly related at a constant volume is Gay-Lussac's Law. This relationship is expressed mathematically as ( P \propto T ) when volume remains constant. This means that if the temperature of a gas increases, the pressure also increases, provided the volume does not change.

This direct relationship arises from the kinetic molecular theory, which suggests that an increase in temperature correlates with an increase in the average kinetic energy of the gas molecules. As the kinetic energy rises, the molecules collide with the walls of their container more forcefully and more frequently, leading to an increase in pressure.

In contrast, Boyle's Law describes the inverse relationship between pressure and volume at constant temperature, while Charles's Law pertains to the direct relationship between volume and temperature at constant pressure. Graham's Law relates to the rates of effusion and diffusion of gases and does not involve any direct correlation with pressure and temperature at constant volume.