# How many grams are in 12 moles of helium?

Just under $50 \cdot g$.
$H e$ has a molar mass of $4.003 \cdot g \cdot m o {l}^{-} 1$.
$\text{Mass} = 4.003 \cdot g \cdot \cancel{m o {l}^{-} 1} \times 12 \cdot \cancel{m o l}$ $=$ ??*g