# What is the ideal gas law constant?

##### 1 Answer
Oct 18, 2014

The ideal gas law constant is a value derived from the volume of one mole of gas at standard temperature and pressure (STP).

Using the equation for the ideal gas law of PV=nRT we can calculate the value of the constant R using the values of a gas at STP.

P = 1 atm
V = 22.4 L (Avogadro's value of 1 mole of gas at STP)
n = 1 mole
R = ???
T = 273 K

(1 atm)(22.4 L) = (1 mol) R (273 K)

$\frac{\left(1 a t m\right) \left(22.4 L\right)}{\left(1 m o l\right) \left(273 K\right)} = R$

$\frac{\left(0.082051 \left(a t m\right) \left(L\right)\right)}{\left(m o l\right) \left(K\right)} = R$

What is most important about this constant is the unit values that allow for the conversion of units in the calculations of the ideal gas law.

There are variations to the gas law constant based upon units used .

$\frac{\left(8.31 \left(k P a\right) \left(L\right)\right)}{\left(m o l\right) \left(K\right)} = R$

and

$\frac{8.31 \left(k P a\right) \left({\mathrm{dm}}^{3}\right)}{\left(m o l\right) \left(K\right)} = R$