Chọn đáp án A
Giải thích:
$\begin{align} & \left\{ \begin{align} & Mg \\ & Al \\ \end{align} \right.+\underbrace{{{O}_{2}}}_{0,125\,mol}\xrightarrow{{}}\underbrace{\left\{ \begin{align} & MgO \\ & A{{l}_{2}}{{O}_{3}} \\ \end{align} \right.}_{9,1\,gam} \\ & BTKL:{{m}_{KL}}=9,1-0,125.32=5,1\,gam...