giải thích dùm mình nha

$\text{Xét}$ `1` `mol` `A_2O_3:`

$m_{O/A_2O_3}$ `=` `16` `.` `3` `=` `48` `(g)`

$m_{A_2O_3}$ `=` `48` `:` `30`$\text{%}$ `=` `160` `(g)`

$m_{A/A_2O_3}$ `=` `160` `-` `48` `=` `112` `(g)`

`M_A` `=` `112` `:` `2` `=` `56` $(g/mol)$

`=>` `A` $\text{là}$ `Fe` `(`$\text{Sắt}$`)`

`=>` $\text{Chọn}$ `D`

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$\text{Kiểm tra lại:}$

$\text{Xét}$ `1` `mol` `BH_4:`

$m_{H/BH_4}$ `=` `1` `.` `4` `=` `4` `(g)`

$m_{BH_4}$ `=` `4` `:` `25`$\text{%}$ `=` `16` `(g)`

`M_B` `=` $m_{B/A_2O_3}$ `=` `16` `-` `4` `=` `12` $(g/mol)$

`=>` `B` $\text{là}$ `C` $(Cacbon)$

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