Ideal Gas Law (Molar Form)

The ideal gas law, expressed as [latex]PV = nRT[/latex], is a cornerstone of thermodynamics and physical chemistry. It was first stated by Benoît Paul Émile Clapeyron in 1834 as a combination of the empirical laws of Boyle, Charles, Gay-Lussac, and Avogadro. This equation of state provides a remarkably accurate approximation for the behavior of many gases under conditions of moderate temperature and low pressure. In the equation, [latex]P[/latex] represents the absolute pressure, [latex]V[/latex] is the volume, [latex]n[/latex] is the number of moles of the gas, and [latex]T[/latex] is the absolute temperature in Kelvin.

The constant of proportionality, [latex]R[/latex], is known as the universal gas constant. Its value is the same for all gases and is approximately 8.314 J/(mol·K). The law’s power lies in its ability to relate the four macroscopic state variables of a gas in a single, simple formula. This allows for the calculation of any one variable if the other three are known. The “ideal” nature of the gas described by this law stems from two key assumptions: the gas particles themselves have negligible volume, and there are no intermolecular attractive or repulsive forces between them. While no real gas is truly ideal, many common gases like nitrogen, oxygen, and argon behave nearly ideally under standard conditions, making the law extremely useful for practical applications.