# In the ideal gas law, what would you use for R when P is in Pascals?

Values (and importantly!) units will be included as supplementary material in any exam you will ever sit. For chemists, $R = 0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1$, the value is usually most useful in that both litres and atmospheres are handy units (more so than ${m}^{3}$ and Pascals).
When pressure is measured in Pascals, $R = 8.314 \cdot {m}^{3} \cdot P a \cdot {K}^{-} 1 m o {l}^{-} 1$. Note here that volume is measured in ${m}^{3}$; $1$ ${m}^{3}$ $=$ $1000$ $L$.