Editing Gas constant (section)

== Dimensions ==
From the ideal gas law ''PV'' = ''nRT'' we get
: <math>R = \frac{PV}{nT},</math>
where ''P'' is pressure, ''V'' is volume, ''n'' is number of moles of a given substance, and ''T'' is [[temperature]].

As pressure is defined as force per area of measurement, the gas equation can also be written as
: <math>R = \frac{ \dfrac{\text{force}}{\text{area}} \times \text{volume} }
                 { \text{amount} \times \text{temperature} }.
</math>

Area and volume are (length)<sup>2</sup> and (length)<sup>3</sup> respectively. Therefore:
: <math>R = \frac{ \dfrac{\text{force} }{ (\text{length})^2} \times (\text{length})^3 }
                 { \text{amount} \times \text{temperature} }
         = \frac{ \text{force} \times \text{length} }
                { \text{amount} \times \text{temperature} }.
</math>

Since force × length = work,
: <math>R = \frac{ \text{work} }
                 { \text{amount} \times \text{temperature} }.
</math>

The physical significance of ''R'' is work per mole per kelvin. It may be expressed in any set of units representing work or energy (such as [[joule]]s), units representing temperature on an absolute scale (such as [[kelvin]] or [[Rankine scale|rankine]]), and any system of units designating a mole or a similar pure number that allows an equation of macroscopic mass and fundamental particle numbers in a system, such as an ideal gas (see [[Avogadro constant]]).

Instead of a mole the constant can be expressed by considering the [[normal cubic metre]].

Otherwise, we can also say that
: <math>\text{force} = \frac{ \text{mass} \times \text{length} }
                            { (\text{time})^2 }.
</math>

Therefore, we can write ''R'' as
: <math>R = \frac{ \text{mass} \times \text{length}^2 }
                 { \text{amount} \times \text{temperature} \times (\text{time})^2 }.
</math>

And so, in terms of [[SI base units]],
: ''R'' = {{physconst|R|unit=kg⋅m<sup>2</sup>⋅s<sup>−2</sup>⋅K<sup>−1</sup>⋅mol<sup>−1</sup>|ref=no}}.