# How many moles are in "4.555 g He"?

$\text{4.555 g He}$ contain $\text{1.1380 mol He}$."
The molar mass of helium (He) is $\text{4.002602 g/mol}$ (relative atomic mass on the periodic table in grams/mol), which means that one mole He has a mass of $\text{4.002602 g}$.
To determine the moles He in $\text{4.555 g He}$, divide the given mass by its molar mass.
$4.555 \cancel{\text{g He"xx(1"mol He")/(4.002602cancel"g He")="1.1380 mol He}}$