To what volume must a liter of oxygen be expanded if the molecules per unit volume is $12 \times 10^{11} \mathrm{~cm}^{-3}$ Diameter of the oxygen molecule $= 3\mathring{\rm{A}}$. Assume that the gas starts at STP. $\left(\mathrm{R}=8.3 \times 10^{7} \text { dynes. cm. mole }{ }^{-1} \mathrm{~K}^{-1}, \mathrm{~N}_{0}=6.02 \times 10^{23} \text { mole }^{-1}\right)$.