In this question, we have to find the density of a sample of Xe gas that has 0.192 moles in a 5.00 L flask, in order to calculate the density, we need to have:
d = m/V
We already have the volume, 5.00 L, but we don't need the mass yet, we will use the number of moles and the molar mass of Xe to find this final mass, the molar mass is 131.293g/mol:
131.293g = 1 mol
x grams = 0.192 moles
x = 25.2 grams of Xe gas
Now we use the formula for density:
d = 25.2/5
d = 5.04 g/L