Cho m gam hỗn hợp $\mathrm{X}$ gồm $\mathrm{Al}, \mathrm{Al}_{2}...

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$\left\{ \begin{array}{*{35}{l}}
x-y=0,3952 \\
3x+y=1,6848 \\
\end{array} \right.$$\to \left\{ \begin{array}{*{35}{l}}
x=0,52 \\
y=0,1248 \\
\end{array} \right.\rightarrow n_{\mathrm{Al}^{3+}}=0,52\text{Al}: 0,12+2a+b=0,5247,265 \%\dfrac{(3 a+3 b) \cdot 16}{27.0,12+102 a+78 b} \cdot 100=47,265\rightarrow\left\{\begin{array}{l}a=0,13 \\ b=0,14\end{array}\right.\rightarrow \% m_{\mathrm{Al}_{2} \mathrm{O}_{3}}=48,36 \%$