Câu 2:
Đặt hóa trị M là x(x>0)
\(PTHH:2M+2xHCl\to 2MCl_x+xH_2\\ \Rightarrow n_{M}=n_{MCl_x}\\ \Rightarrow \dfrac{19,5}{M_M}=\dfrac{40,8}{M_M+35,5x}\\ \Rightarrow M_M=32,5x\)
Thay \(x=2\Rightarrow M_M=65(g/mol)\)
Vậy M là kẽm (Zn)
Câu 3:
Đặt \(n_{Al}=x(mol);n_{Mg}=y(mol)\)
\(\Rightarrow 27x+24y=6,3(1)\\ n_{H_2}=\dfrac{6,72}{22,4}=0,3(mol)\\ PTHH:2Al+6HCl\to 2AlCl_3+3H_2\\ Mg+2HCl\to MgCl_2+H_2\\ \Rightarrow 1,5x+y=0,3(2)\\ (1)(2)\Rightarrow x=0,1;y=0,15(mol)\\ \Rightarrow m_{Al}=0,1.27=2,7(g)\\ m_{Mg}=0,15.24=3,6(g)\)