# What are some common mistakes students make with the molar volume of a gas?

${V}_{m} = \frac{V}{n} = \frac{R T}{P}$.
Choice of $R$, the gas constant with the appropriate units, is an error I still am prone to make (hopefully not here). The choice of units does not help. Litres would reasonably be the most useful choicefor the practising chemist . The gas constant is ??.
$R$ = $0.0821$ $\frac{L \cdot a t m}{m o l \cdot K}$.
Of course, the pressure might not be quoted in atmospheres, but in kilopascals, and so, $R$ $=$ $8.31 \cdot J \cdot m o {l}^{- 1} {K}^{- 1}$. It is hard to convert this dimensionally to units of pressure.