X có thể phản ứng trực tiếp với ${{H}_{2}}$, ${{O}_{2}}$ và Fe $\Rightarrow $X chỉ có thể là Lưu huỳnh (S)
(1) $\begin{align}
& \,\,\,S+{{H}_{2}}\xrightarrow{t{}^\circ }{{H}_{2}}S\uparrow \\
& (X)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(A) \\
\end{align}$
(2) $\begin{align}
& 2{{H}_{2}}S+{{O}_{2}}\to 2S+2{{H}_{2}}O \\
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(D) \\
\end{align}$
(3) $\begin{align}
& S+{{O}_{2}}\xrightarrow{t{}^\circ }S{{O}_{2}}\uparrow \\
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(B) \\
\end{align}$
(4) $\begin{align}
& SO{}_{2}+B{{r}_{2}}+2{{H}_{2}}O\to {{H}_{2}}S{{O}_{4}}+2HBr \\
& (B)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(D)\,\,\,\,\,\,\,\,\,\,\,\,\,(Y)\,\,\,\,\,\,\,\,\,\,\,(Z) \\
\end{align}$
(5) $\begin{align}
& S+Fe\xrightarrow{t{}^\circ }FeS \\
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(E) \\
\end{align}$
(6) $\begin{align}
& FeS+{{H}_{2}}S{{O}_{4}}\to FeS{{O}_{4}}+{{H}_{2}}S \\
& (E)\,\,\,\,\,\,\,\,\,(Y)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(G)\,\,\,\,\,\,\,\,\,\,\,(A) \\
\end{align}$
$\begin{align}
& FeS+2HBr\to FeB{{r}_{2}}+{{H}_{2}}S \\
& (E)\,\,\,\,\,\,\,\,\,\,\,(Z)\,\,\,\,\,\,\,\,\,\,\,(G)\,\,\,\,\,\,\,\,\,(A) \\
\end{align}$