Ideal gas

Ideal gas

The ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated by Émile Clapeyron in 1834 as a combination of the empirical Boyle's law, Charles' law and Avogadro's Law.^[1] The ideal gas law is often written as:

where:

· P is the pressure of the gas

· n is the amount of substance of gas (in moles)· V is the volume of the gas

· R is the ideal, or universal, gas constant, equal to the product of the Boltzmann constant and the Avogadro constant.

· T is the temperature of the gas

Molar form

How much gas is present could be specified by giving the mass instead. The chemical amount (n) (in moles) is equal to the mass (m) (in grams) divided by the molar mass (M) (in grams peof the chemical amount of gas. Therefore, an alternative form of the ideal gas law may be useful.

r mole):

Defining the specific gas constant R_specific as the ratio R/M,

This form of the ideal gas law is very useful because it links pressure, density, and temperature in a unique formula independent of the quantity of the considered gas. Alternatively, the law may be written in terms of the specific volume v, the reciprocal of density, as

It is common, especially in engineering applications, to represent the specific gas constant by the symbol R. In such cases, the universal gas constant is usually given a different symbol such as R to distinguish it. In any case, the context and/or units of the gas constant should make it clear as to whether the universal or specific gas constant is being referred to.