Mol He in the mixture = 2
Further explanation
Given
50% by mass
2.2 moles of mixture
Required
The mole number of He
Solution
50% by mass⇒ mass of He : mass of Ar = 1 : 1
Mol He = 2.2 - mol Ar
mass He = mass Ar
mol x MW He = mol x MW Ar
(2.2-mol Ar) x 4 = mol Ar x 40
8.8 - 4 mol Ar = 40 mol Ar
8.8 = 44 mol Ar
mol Ar= 0.2
mol He = 2.2 - 0.2 = 2
