Дано
w(Fe) = 72.46 = 0.7246
Решение
FexOy
w(Fe) = xAr(Fe) / (xAr(Fe) + yAr(O))
0.7246 = 56x / (56x + 16y)
0.7246 (56x + 16y) = 56x
0.7246 (56x + 16y) = 56x
40.5776x + 11.5936y = 56x
11.5936y = 56x - 40.5776x
11.5936y = 15.4224x
y = 1.33x
3y = 4x
x : y = 3 : 4
Ответ: Fe3O4