# What mass is associated with 23*mol of methane?

Well, each mole of methane CLEARLY contains $12.011 \cdot g$ of carbon by mass.
And in $23$ $m o l$ of $\text{methane}$, there are $23 \cdot \cancel{m o l} \times 12.011 \cdot g \cdot \cancel{m o {l}^{-} 1} = 276.25 \cdot g$.