a. ta có CTHH: \(Fe^{III}_xO^{II}_y\)
\(\rightarrow III.x=II.y\rightarrow\dfrac{x}{y}=\dfrac{II}{III}=\dfrac{2}{3}\rightarrow\left\{{}\begin{matrix}x=2\\y=3\end{matrix}\right.\)
\(\rightarrow CTHH:Fe_2O_3\)
\(PTK=2.56+3.16=160\left(đvC\right)\)
b. ta có CTHH: \(Al^{III}_x\left(OH\right)^I_y\)
\(\rightarrow III.x=I.y\rightarrow\dfrac{x}{y}=\dfrac{I}{III}=\dfrac{1}{3}\rightarrow\left\{{}\begin{matrix}x=1\\y=3\end{matrix}\right.\)
\(\rightarrow CTHH:Al\left(OH\right)_3\)
\(PTK=27+\left(16+1\right).3=78\left(đvC\right)\)