Em tham khảo nha :
\(\begin{array}{l}
2A + 2xHCl \to 2AC{l_x} + x{H_2}\\
{n_{{H_2}}} = \dfrac{{2,688}}{{22,4}} = 0,12mol\\
{n_A} = \dfrac{{2{n_{{H_2}}}}}{x} = \dfrac{{0,24}}{x}mol\\
{M_A} = 7,8:\dfrac{{0,24}}{x} = 32,5x\,dvC\\
x = 2 \Rightarrow {M_A} = 65dvC\\
\Rightarrow A:\text{ Kẽm}(Zn)\\
{n_{HCl}} = 2{n_{{H_2}}} = 0,24mol\\
B:\text{Kẽm oxit}(ZnO)
\end{array}\)