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The gas constant is the constant of proportionality that relates the energy scale in physics to the temperature scale and the scale used for amount of substance. Thus, the value of the gas constant ultimately derives from historical decisions and accidents in the setting of units of energy, temperature and amount of substance.
These include the Boltzmann constant, which gives the correspondence of the dimension temperature to the dimension of energy per degree of freedom, and the Avogadro constant, which gives the correspondence of the dimension of amount of substance with the dimension of count of entities (the latter formally regarded in the SI as being dimensionless).
Some constants, such as the ideal gas constant, R, do not describe the state of a system, and so are not properties. On the other hand, some constants, such as K f (the freezing point depression constant, or cryoscopic constant ), depend on the identity of a substance, and so may be considered to describe the state of a system, and therefore ...
energy: joule (J) Young's modulus: pascal (Pa) or newton per square meter (N/m 2) eccentricity: unitless Euler's number (2.71828, base of the natural logarithm) unitless electron: unitless elementary charge: coulomb (C) force: newton (N) Faraday constant: coulombs per mole (C⋅mol −1)
Therefore, the kinetic energy per kelvin of one mole of monatomic ideal gas (D = 3) is = =, where is the Avogadro constant, and R is the ideal gas constant. Thus, the ratio of the kinetic energy to the absolute temperature of an ideal monatomic gas can be calculated easily:
Hence, all the energy possessed by the gas is the kinetic energy of the molecules, or atoms, of the gas. = This corresponds to the kinetic energy of n moles of a monoatomic gas having 3 degrees of freedom; x, y, z. The table here below gives this relationship for different amounts of a monoatomic gas.
By the equipartition theorem, internal energy per mole of gas equals c v T, where T is absolute temperature and the specific heat at constant volume is c v = (f)(R/2). R = 8.314 J/(K mol) is the universal gas constant, and "f" is the number of thermodynamic (quadratic) degrees of freedom, counting the number of ways in which energy can occur.
In other words, that theory predicts that the molar heat capacity at constant volume c V,m of all monatomic gases will be the same; specifically, c V,m = 3 / 2 R. where R is the ideal gas constant, about 8.31446 J⋅K −1 ⋅mol −1 (which is the product of the Boltzmann constant k B and the Avogadro constant).