# How do you find the ideal gas constant?

Mar 20, 2014

The ideal gas law uses the formula PV = nRT where P is the pressure in atmospheres (atm), V is the volume in liters (L), n is the number of moles (mol) and T is the temperature in kelvin (K).

If we set up the ideal gas law for the values of 1 mole at Standard temperature and pressure (STP) and calculate for the value of the constant R, we can determine the value of the ideal gas law constant.

P = 1 atm
V = 22.4 L (Avogadro's number)
n = 1 mol
R = Constant
T = 273 K (0 C)

Isolating the R value the equation is

$\frac{P V}{n T} = R$

$\frac{\left(1 a t m\right) \left(22.4 L\right)}{\left(1 m o l\right) \left(273 K\right)} = 0.08205 \frac{\left(a t m\right) \left(L\right)}{\left(m o l\right) \left(K\right)}$