# What is the pressure in a 10.6-L cylinder filled with 11.2 g of oxygen gas at a temperature of 345 K?

Approx. $\text{1 atm}$
We use the Ideal gas equation with appropriate units. $R = 0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1$, is probably most useful for chemists.
$P = \frac{n R T}{V}$ $=$ $\frac{\frac{11.2 \cdot \cancel{g}}{32.0 \cdot \cancel{g} \cdot \cancel{m o {l}^{-} 1}} \cdot 0.0821 \cdot \cancel{L} \cdot a t m \cdot \cancel{{K}^{-} 1} \cdot \cancel{m o {l}^{-} 1} \times 345 \cdot \cancel{K}}{10.6 \cdot \cancel{L}}$ $\cong$ $1 \cdot a t m$
The most difficult part of this question is choosing the most appropriate gas constant, $R$. For chemists, $R = 0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1$ is probably most useful, because it uses the units that with which chemists typically deal. In an examination, several values of the gas constant should be quoted as supplementary material.