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\begin{document}
\hfill Molar Mass and Molecular Formula of a Gas\hfill\llap{Wed, June 6th, 2007}
\begin{enumerate}[leftmargin=0in,nosep]
\item Assume 100g of sample of gas \\[\baselineskip]
\begin{tabular}{cccl}
Element & mass(g) & moles(mol) & ratio \\
\ce{C} & \text{80 g} & \text{6.67 mol} & $\mathrm{1\times2=2}$ \\
\ce{H2} & \text{20 g} & \text{10 mol} & $\mathrm{1.5\times2=3}$ \\
\end{tabular}
\end{enumerate}
\end{document}