дано
Fe3O4
-----------------
W(Fe)-?
M(Fe) = 56 g/mol
M(Fe3O4) = 56*3+ 16*4 = 232 g/mol
W(Fe) = 56 / 232 * 100% = 24.14%
ответ 24.14%
дано
FeO
-----------------
W(Fe)-?
M(Fe) = 56 g/mol
M(FeO) = 56+ 16 = 72 g/mol
W(Fe) = 56 / 72 * 100% = 77.78%
ответ 77.78%