# In the ideal gas law equation, PV=nRT, what is the value of the variable 'R'?

The Gas constant $R$ changes according to the units you employ.
Chemists typically deal with $\text{litre}$ quantities of gases, and typically measure $\text{pressure}$ in units of $\text{atmospheres}$. Of course, both physicists and chemists tend to use $\text{degrees Kelvin}$ as units of absolute temperature (mind you, there is a $\text{Rankin}$ scale).
Given this, for chemists, $R$ is typically used as $0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1$. There are other conventions, notably, $R = 8.31 \cdot J \cdot {K}^{-} 1 \cdot m o {l}^{-} 1$, which requires volumes in ${m}^{3}$. All of the gas constants, and their units, should be supplied to you in an exam as supplementary material.