American Chemical Society (ACS) Chemistry Test 2025 – 400 Free Practice Questions to Pass the Exam

Gay-Lussac's Law asserts that the pressure of a gas is directly proportional to its absolute temperature when the volume of the gas is held constant. This means that as the temperature of the gas increases, the pressure also increases provided the volume doesn't change. In the context of the question, it’s essential that the volume remains constant to establish a clear relationship between pressure and temperature.

When other factors like mass, density, or amount of substance are considered, they could potentially change the behavior of the gas in relation to pressure and temperature. For instance, if the amount of substance changes, it would alter the pressure as well due to the introduction of more gas molecules. Similarly, a change in density could result from a change in volume or temperature, thus complicating the ability to clearly observe the relationship described by Gay-Lussac's Law.

By holding the volume constant, one can isolate the effects of temperature on pressure, making it possible to express a direct relationship that is fundamental to thermodynamic principles in gases.