Calculate the mass percent of Oxygen

Question

Calculate the mass percent of Oxygen in

Sethium Oxide (St2 O3) using the masses shown below:

St - 192.09

O - 15.999

Answer 1

This is apparently a fictitious compound, as Sethium is not an element that appears on the periodic table of elements. That being said, we can calculate the % oxygen in St₂O₃ as follows:

molar mass St2O3 = (192.09 x 2) + (15.999 x 3) = 384.18 + 47.997 = 432.18 g / mole

% O = 47.997 / 432.18 (x100%) = 11.106%