Consider a vapour-liquid mixture of components $A$ and $B$ that obeys Raoult's law. The vapour pressure of $A$ is half that of $B$. The vapour phase concentrations of $A$ and $B$ are $3 \mathrm{~mol} \mathrm{~m}^{-3}$ and $6 \mathrm{~mol} \mathrm{~m}^{-3}$, respectively. At equilibrium, the ratio of the liquid phase concentration of $A$ to that of $B$ is
- $1.0$
- $0.5$
- $2.0$
- $1.5$