Lời giải:Đáp án B
\(m\left\{ \begin{array}{l}
Na:x\\
Ba:y\\
Al:6{\rm{x}}
\end{array} \right. \to \left\{ \begin{array}{l}
A{l_{du}}:5,4 \to n = 0,2\\
{H_2}:0,8\\
\left\{ \begin{array}{l}
NaAl{O_2}:x\\
Ba{\left( {Al{O_2}} \right)_2}:y
\end{array} \right.
\end{array} \right.\)
\(\begin{array}{l}
Na \to N{a^ + } + 1e\\
2{H^ + } + 2e \to {H_2}\\
Ba \to B{a^{2 + }} + 2e\\
Al \to A{l^{3 + }} + 3e\\
{n_{Al{\rm{ phan ung}}}} = {n_{NaAl{O_2}}} + 2{n_{Ba{{\left( {Al{O_2}} \right)}_2}}} = x + 2y
\end{array}\)
BT Al: 6x = 0,2 + x + 2y
BT e: \(x + 2y + 3\left( {x + 2y} \right) = 0,8.2\)
\( \to \left\{ \begin{array}{l}
x = 0,1\\
y = 0,15
\end{array} \right. \to m\left\{ \begin{array}{l}
Na:0,1\\
Ba:0,15\\
Al:0,6
\end{array} \right. \to m = 39,05\)(g).
