The above equation is basically a simple equation of state (EOS). Where Z is the gas compressibility factor, which is a useful thermodynamic property for modifying the ideal gas law to account for behavior of real gases. For such gases, the simplest method of determining molar volumes is by using compressibility factors as in the following expression: Real gases are those gases that do not exhibit ideal gas behavior. The relationship between the two constants is R s = R / M where M is the molecular mass of the gas. The technical literature can be confusing because some authors often fail to explain whether they are using the universal gas law constant R, which applies to any ideal gas, or whether they are using the specific gas law constant R s, which only applies to a specific individual gas.°R is degrees Rankine (an absolute temperature scale) and ☏ is degrees Fahrenheit (a temperature scale).lb-mol is an abbreviation for pound-mol.°R -1Įxample calculations of ideal gas molar volumes:.= the universal gas law constant of 10.7316 ft 3 = the gas absolute temperature, in degrees Rankine (°R) = the universal gas law constant of 8.314472 m 3 The ideal gas law equation can be rearranged to give this expression for the molar volume of an ideal gas: Otherwise, the numerical values are meaningless. When stating molar volume numerical values, it is important to also state the given conditions of temperature and pressure.

Where x i is the mole fraction of the ith component, M i is the molecular mass of the ith component and ρ mixture is the mixture density at the given temperature and pressure. If a substance is a mixture containing N components, the molar volume is calculated using: However, molar volumes are often expressed as cubic metres per 1,000 moles (m 3/kmol) or cubic decimetres per mol (dm 3/mol) for gases and as centimetres per mole (cm 3/mol) for liquids and solids. It has an SI unit of cubic metres per mole (m 3/mol). It is equal to the molecular mass ( M) of the substance divided by its density ( ρ) at the given temperature and pressure:

The molar volume (symbol V m) of a substance is the volume occupied by one mole of the substance at a given temperature and pressure.

Molar volume