Gas Constants

Gas Constants

• Universal Gas Constant R*
• Individual Gas Constant Ri

The gas constant provides a proportional relationship between the kinetic energy of the molecules in a gas and the temperature of the gas.

Universal Gas Constant R*

The Universal Gas Constant (R*) is common to all gases and its value is dependent on the units use to describe the rest of the ideal gas law equation.

In SI units, the universal gas constant value is R* = 8.314462175 J / mol.K

Table of universal gas constant in different units:

Individual Gas Constant Ri

The Individual Gas Constant (Ri) is dependent on the molar mass of the particular gas and can be calculated from the Universal Gas Constant as follows:

Formula:	Ri = R* / M
	Ri = individual gas constant (J/Kg.K, ft.lb/slugs.°R) R* = universal gas constant (J/mol.K, ft.lb/lb-mol.°R) M = molecular weight of the ideal gas or mixture of gases (kg, slugs)

Table of common gases and their individual gas constants: