Answer
There are 6.5 moles of helium in 13 grams of helium.
Work Step by Step
A helium atom consists of 1 proton and 1 neutron.
The mass of one helium atom is $2~u$
We know that 1 mole of helium has a mass of $2~g$. We can find the number of moles in $13~g$ of helium:
$\frac{13~g}{2~g/mol} = 6.5~mol$
There are 6.5 moles of helium in 13 grams of helium.
