gasconstante

The gas constant, denoted R, is a fundamental physical constant that appears in thermodynamics and chemistry, most notably in the ideal gas law PV = nRT. It relates the macroscopic properties of a gas—pressure, volume, temperature, and amount of substance—and serves as a proportionality factor that depends on the units used.

In the International System of Units (SI), R equals 8.314462618 joule per mole per kelvin (J·mol−1·K−1). In other unit systems, it has other published values, such as 0.082057366 L·atm·mol−1·K−1, 1.9872041 cal·mol−1·K−1, or 0.08314 L·bar·mol−1·K−1. The constant is related to the Boltzmann constant kB by R = N_A · kB, where N_A is Avogadro’s number.

For a specific gas with molar mass M, a specific gas constant Rs can be defined as Rs = R / M. This form is used in equations of state and thermodynamic calculations for a particular substance, linking energy scales to mass.

Applications of the gas constant span chemistry, physics, engineering, and atmospheric science. It underpins calculations of gas densities, energy per mole at a given temperature, and properties derived from the ideal gas law, while also informing real-gas corrections. CODATA periodically provides recommended values with uncertainties to support precise computations.