Some comments on the ideal gas constant $R$

 The constant $R$ in the ideal gas equation of state may have different values according to the unit system in use. For example

$R$	Units
SI units
8.314	$J\,K^{−1}\,mol^{−1}$
8.314	$m^3\,Pa\,K^{−1}\,mol^{−1}$
8.314	$kg\,m^2\,s^{-2}\,K^{−1}\,mol^{−1}$
Other units
8314.462	$L\,Pa\,K^{−1}\,mol^{−1}$
8.314	$L\,kPa\,K^{−1}\,mol^{−1}$
$8.314\times10^{-2}$	$L\,bar\,K^{−1}\,mol^{−1}$
$8.314\times10^{7}$	$erg\,K^{−1}\,mol^{−1}$
$7.302\times10^{-1}$	$atm\,ft^3\,lb_{mol}^{−1}\,R^{−1}$
10.731	$psi\,ft^3\,lb_{mol}^{−1}\,R^{−1}$
1.986	$BTU\,lb_{mol}^{−1}\,R^{−1}$
297.031	$inH_2O\,ft^3\,lb_{mol}^{−1}\,R^{−1}$
554.984	$torr\,ft^3\,lb_{mol}^{−1}\,R^{−1}$
$8.206\times10^{-2}$	$L\,atm\,K^{−1}\,mol^{−1}$
62.363	$L\,torr\,K^{−1}\,mol^{−1}$
1.987	$cal\,K^{−1}\,mol^{−1}$
$8.206\times10^{-5}$	$m^3\,atm\,K^{−1}\,mol^{−1}$

However, as you may imagine if a gas in question has an idealized behavior then the constant $R$ may apply. A gas behaves as an ideal gas under certain conditions of pressure, $P=0$, and temperature so that the following equation of state applies

$PV=nRT$

One way to check for the constant $R$ for any given gas is in a plot of $PV/nT$ versus $P$ which should be a straight line. Also, when this line cuts the vertical axis ($PV/nT$) at $P=0$ you should read any of the values of the table above (according to the units you were using).

Other stuff of interest

• LE01 - AC and DC voltage measurement and continuity test
• LE 02 - Start and stop push button installation 24V DC
• What is an Equation of State
• Minor losses  - Formulas
• What is a process variable?
• What are the most important process variables?
• Time dependence of process variables
• A list of process variables

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Ildebrando.