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) $\begin{align} & FeS+{{H}_{2}}S{{O}_{4}}\to FeS{{O}_{4}}+{{H}_{2}}S \\ & (E)\,\,\,\,\,\,\,\,\,(Y)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(G)\,\,\,\,\,\,\,\,\,\,\,(A) \\ \end{align}$
$\begin{align} & FeS+2HBr\to FeB{{r}_{2}}+{{H}_{2}}S \\ & (E)\,\,\,\,\,\,\,\,\,\,\,(Z)\,\,\,\,\,\,\,\,\,\,\,(G)\,\,\,\,\,\,\,\,\,(A) \\ \end{align}$