The mole fraction of He in a gaseous solution prepared from 1.0 g of He,6.5 g of Ar,and 10.0 g of Ne is ________.
A)0.28
B)0.25
C)0.20
D)0.66
E)0.86

Question

Quizplus · Accepted Answer

The mole fraction of a component in a mixture is the ratio of the number of moles of that component to the total number of moles of all components in the mixture. To find the mole fraction of He, we first calculate the moles of each gas using their molar masses (He = 4 g/mol, Ar = 39.95 g/mol, Ne = 20.18 g/mol), then divide the moles of He by the total moles.Moles of He = 1.0 g / 4 g/mol = 0.25 molMoles of Ar = 6.5 g / 39.95 g/mol = 0.163 molMoles of Ne = 10.0 g / 20.18 g/mol = 0.496 molTotal moles = 0.25 mol + 0.163 mol + 0.496 mol = 0.909 molMole fraction of He = 0.25 mol / 0.909 mol ≈ 0.275The closest answer to this calculation is 0.28, so the correct choice is A.

The Mole Fraction of He in a Gaseous Solution Prepared