CTHH: \(Fe^{III}_xO_y^{II}\)
Theo quy tắc hóa trị: III.x = II.y
=> \(\dfrac{x}{y}=\dfrac{II}{III}=\dfrac{2}{3}\)
=> CTHH: Fe2O3
CTHH: \(Na^I_x\left(SO_4\right)^{II}_y\)
Theo quy tắc hóa trị: I.x = II.y
=> \(\dfrac{x}{y}=\dfrac{II}{I}=\dfrac{2}{1}\)
=> CTHH: Na2SO4