Đáp án:
\(\begin{array}{l}
\begin{array}{*{20}{l}}
{4Fe{S_2}}& + &{11{O_2}}& \to &{2F{e_2}{O_3}}& + &{8S{O_2}}
\end{array}\\
F{e_2}{O_3}\; + \;6NaHS{O_4}\; \to F{e_2}{\left( {S{O_4}} \right)_3}\; + \;3N{a_2}S{O_4}\; + \;3{H_2}O\\
N{a_2}S{O_4} + BaC{l_2} \to BaS{O_4} + 2NaCl
\end{array}\)