In the mineral pyrite, 7 g of iron contains 8 g of sulfur. Calculate the mass fractions of each element

In the mineral pyrite, 7 g of iron contains 8 g of sulfur. Calculate the mass fractions of each element in this substance and determine its formula.

1. Let’s denote the formula of a substance using the indices x, y:
FexSу
2.m (FexSу) = m (Fe) + m (S) = 7 + 8 = 15 g
3.w (Fe) = 7/15 = 0.4667 or 46.67%
4.w (S) = 8/15 = 0.5333 or 53.33%
5. Find the ratio of the indices
x: y = w (Fe) / Ar (Fe): w (S) / Ar (S) = 0.4667 / 56: 0.5333 / 32 =
= 0.00833: 0.01667
6. Determine the value of the indices
x: y = 0.00833 / 0.00833: 0.01667 / 0.00833 = 1: 2
Answer: the formula of the substance FeS2