Silicon tetrachloride $\left(\mathrm{SiCl}_{4}\right)$ can be prepared by heating $\mathrm{Si}$ in chlorine gas:$$\mathrm{Si}(s)+2 \mathrm{Cl}_{2}(g) \longrightarrow \mathrm{SiCl}_{4}(l)$$In one reaction, 0.507 mole of $\mathrm{SiCl}_{4}$ is produced. How many moles of molecular chlorine were used in the reaction?