Answer
Mass percentage of Ne in the sample of gas mixture is 44.8 %.
Mass percentage of Kr in the sample of gas mixture is 55.2 %.
Work Step by Step
Strategy: Convert moles to mass by using conversion factor Molar mass/ 1 mol. Then find the total mass of the mixture by adding the masses of Ne and Kr. Lastly find the percentage mass of Ne and Kr in the alloy.
1- Mass of 0.0856 mol Ne
Molar mass of Ne= 20.179 g/mol
0.0856 mol Ne x $\frac{20.179g}{1 mol}$ = 1.7273 g
Mass of 0.0856 mol Ne is 1.7273 g.
Mass of 0.0254 mol Kr
Molar mass of Kr = 83.798 g/mol
0.0254 mol Kr x $\frac{83.798}{1 mol}$ =2.1285 g
Mass of 0.0254 mol Kr is 2.1285 g.
2- The total mass of mixture is: mass Ne + mass Kr.
So the total mass is 1.7273 g + 2.1285 g = 3.8558 g.
3- Mass percentage of Ne in the sample of gas mixture= $\frac{1.7273 g (Ne )}{3.8558 g(mixture)}$ $\times$ 100%
Mass percentage of Ne in the sample of gas mixture = 0.44798 $\times$ 100%
Mass percentage of Ne in the sample of gas mixture is 44.8 % ( to three significant figures).
Mass percentage of Kr in the sample of gas mixture = $\frac{0.2.185 g (Kr)}{3.8558 g(mixture)}$ $\times$ 100%
Mass percentage of Kr in the sample of gas mixture = 0. 5520 $\times$ 100%
Mass percentage of Kr in the sample of gas mixture is 55.2 % ( to three significant figures).
