What percentage of the 22.4 liter volume is occupied by helium gas molecules?

The molar volume of an ideal gas at STP is
22.4

d
m
3
, or
22.4

L
.
Explanation:
In one mole of gas there are Avogadro's number of particles. There are
6.022

×

10
23

particles mol
−
1
.
So how many moles are there in
4.02
×
10
22
helium particles?
It is simply the quotient:
4.02
×
10
22
helium particles
6.022
×
10
23
helium particles mol
−
1
=

?
?
m
o
l
The volume of course is the prior quotient mulitplied by the molar volume of an ideal gas:
4.02
×
10
22
helium particles
6.022
×
10
23
helium particles mol
−
1

×

22.4
⋅
L
⋅
m
o
l
−
1