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The molar gas constant (also known as the gas constant, universal gas constant, or ideal gas constant) is denoted by the symbol R or R. It is the molar equivalent to the Boltzmann constant , expressed in units of energy per temperature increment per amount of substance , rather than energy per temperature increment per particle .
molar gas constant: 8.314 462 618 153 24 J⋅mol −1 ⋅K −1: 0 [50] = ... While the values of the physical constants are independent of the system of units in use ...
Macroscopically, the ideal gas law states that, for an ideal gas, the product of pressure p and volume V is proportional to the product of amount of substance n and absolute temperature T: =, where R is the molar gas constant (8.314 462 618 153 24 J⋅K −1 ⋅mol −1). [4]
The ideal gas equation can be rearranged to give an expression for the molar volume of an ideal gas: = = Hence, for a given temperature and pressure, the molar volume is the same for all ideal gases and is based on the gas constant: R = 8.314 462 618 153 24 m 3 ⋅Pa⋅K −1 ⋅mol −1, or about 8.205 736 608 095 96 × 10 −5 m 3 ⋅atm⋅K ...
Note that the especially high molar values, as for paraffin, gasoline, water and ammonia, result from calculating specific heats in terms of moles of molecules. If specific heat is expressed per mole of atoms for these substances, none of the constant-volume values exceed, to any large extent, the theoretical Dulong–Petit limit of 25 J⋅mol ...
The values have been updated to the CODATA 2022 values. This includes the 2019 revision of the SI , which made the values of several constants exact (e.g. e ), whereas some previously exactly defined constants acquired an uncertainty (e.g. μ 0 ).
The relationship between the two constants is R s = R / m, where m is the molecular mass of the gas. The US Standard Atmosphere (USSA) uses 8.31432 m 3 ·Pa/(mol·K) as the value of R. However, the USSA in 1976 does recognize that this value is not consistent with the values of the Avogadro constant and the Boltzmann constant. [49]
The value obtained this way is said to be the molar heat capacity at constant volume (or isochoric) and denoted c V,m, c v,m, c v,m, etc. The value of c V,m is always less than the value of c P,m. This difference is particularly notable in gases where values under constant pressure are typically 30% to 66.7% greater than those at constant ...