\(R+nHCl\rightarrow RCl_n+\frac{n}{2}H_2\)
Ta có:
\(n_{H2}=0,345\left(mol\right)\Rightarrow n_R=\frac{0,69}{n}\)
\(\Rightarrow R=9n\)
\(n=3\Rightarrow R=27\)
Mặt khác \(\left\{{}\begin{matrix}a+b=0,5\\24a+27b=12,6\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}a=0,2\\b=0,3\end{matrix}\right.\)
Vậy R là Al