# How many moles are in 20.0 g He?

Apr 20, 2016

The molar mass of helium is $\text{4.0026 g/mol}$ (atomic mass from the periodic table in g/mol).
$20.0 \cancel{\text{g He"xx(1"mol He")/(4.0026cancel"g He")="5.00 mol He}}$ rounded to three significant figures