What does the perfect gas equation pV = nRT describe?

The ideal gas equation, represented as pV = nRT, describes the behavior of ideal gases, which are hypothetical gases that perfectly follow this equation under all conditions. This equation relates the pressure (p) and volume (V) of a gas to the number of moles (n) and the temperature (T) measured in Kelvin, with R being the universal gas constant.

This relationship is based on certain assumptions about gas behavior: that gases consist of a vast number of tiny particles in constant, random motion, that the volume occupied by individual gas molecules is negligible compared to the volume of the container, and that there are no intermolecular forces acting between the molecules. Under conditions of high temperature and low pressure, real gases tend to behave similarly to ideal gases, allowing the perfect gas equation to be a useful approximation and model for understanding gas behavior in thermodynamic processes.

The remaining options do not pertain to the ideal gas equation. Real gases sometimes exhibit behaviors that deviate from the ideal equation due to intermolecular forces and the volume occupied by molecules, hence they do not fit the description provided by the perfect gas equation. Liquids and superconductors fundamentally behave differently regarding their physical properties, and thus cannot be described by the ideal gas law.