360 cm$^3$ of a hydrocarbon diffuses in 30 minutes, while under the same conditions 360 cm$^3$ of SO$_2$ gas diffuses in one hour. The molecular formula of the hydrocarbon is
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Graham’s law tips:
\begin{itemize}
\item Faster diffusion $\Rightarrow$ lighter gas
\item Rate $\propto 1/\sqrt{M}$
\item Use time ratios for equal volumes
\end{itemize}