# What is the mass of .5 mole of calcium atoms?

Approx. $20 \cdot g$
$1$ $\text{mole}$ of calcium atoms have a mass of $40.08 \cdot g \cdot m o l$. It follows that $0.5 \cdot m o l \times 40.08 \cdot g \cdot m o {l}^{-} 1$ $=$ ??g.