Cho 19,6 gam hỗn hợp rắn X gồm Mg,

* Hướng dẫn giải

Chọn đáp án A

Gọi: $\mathrm{19,6}\left\{\begin{array}{l}Mg:a\\ F{e}_3{O}_4:b\\ Fe{\left(N{O}_3\right)}_2:c\end{array}\right.\stackrel{}{\to }\left\{\begin{array}{l}\stackrel{BTNT.N}{\to }{n}_{N{H}_4^{+}}=2c-\mathrm{0,06}\\ \stackrel{BTKL}{\to }24a+232b+180c=\mathrm{19,6}\end{array}\right.$

$\stackrel{H^{+}}{\to }4b.2+10(2c-\mathrm{0,06})+\mathrm{0,06.4}=\mathrm{0,76}$

$\stackrel{BTE}{\to }2a+b+c=\mathrm{0,06.3}+8(2c-\mathrm{0,06})$

$\stackrel{}{\to }\left\{\begin{array}{l}a=\mathrm{0,13}\\ b=\mathrm{0,04}\\ c=\mathrm{0,04}\end{array}\right.\stackrel{}{\to }m=\mathrm{24,66}\left\{\begin{array}{l}Fe{\left(OH\right)}_3:\mathrm{0,16}\\ Mg{\left(OH\right)}_2:\mathrm{0,13}\end{array}\right.$