Đáp án đúng: B
Fe2O3.
$\displaystyle \begin{array}{l}\text{2,4}\,\text{gam}\left\{ \begin{array}{l}\text{CuO}\,\text{(n}\,\text{mol)}\\\text{F}{{\text{e}}_{\text{x}}}{{\text{O}}_{\text{y}}}\,\text{(n}\,\text{mol)}\end{array} \right.\xrightarrow{{}}\text{1,76}\,\text{gam}\,\left\{ \begin{array}{l}\text{Cu}\\\,\,\text{Fe}\,\,\text{+}\,\,\text{2HCl}\,\xrightarrow{{}}FeC{{l}_{2}}\,+\,{{H}_{2}}\\0,02\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\xleftarrow{{}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,0,02\,mol\end{array} \right.\\\Rightarrow {{\text{m}}_{\text{Fe}}}\,\text{=}\,\text{1,12}\,\text{gam}\Rightarrow {{\text{m}}_{\text{Cu}}}\text{=0,64}\,\text{gam}\Rightarrow \text{n=0,01}\,\text{mol}\\{{\text{n}}_{\text{Fe}}}\text{=n}\text{.x=0,02}\Rightarrow \text{x=2}\Rightarrow \text{F}{{\text{e}}_{\text{2}}}{{\text{O}}_{\text{3}}}\end{array}$
