$\text{Câu 1 :}$
$n_{H_2}=\dfrac{4,48}{22,4}=0,2mol$
$a.Fe+2HCl\to FeCl_2+H_2↑$
$\text{Cu không phản ứng với HCl}$
$\text{b.Theo pt :}$
$n_{Fe}=n_{H_2}=0,2mol$
$⇒m_{Fe}=0,2.56=11,2g$
$\%m_{Fe}=\dfrac{11,2}{30,4}.100\%=36,84\%$
$\%m_{Cu}=100\%-36,84\%=63,16\%$
$n_{HCl}=2.n_{H_2}=0,2.2=0,4mol$
$⇒C_{M_{HCl}}=\dfrac{0,4}{0,5}=0,8M$
$\text{Câu 2 :}$
$a.Mg+2HCl\to MgCl_2+H_2↑$
$\text{Cu không phản ứng với HCl}$
$b.m_{rắn}=m_{Cu}=1,28g$
$⇒\%m_{Cu}\dfrac{1,28}{20,488}.100\%=6,25\%$
$\%m_{Mg}=100\%-6,25\%=93,75\%$
$c.m_{Mg}=20,488-1,28=19,208g$
$⇒n_{Mg}=\dfrac{19,208}{24}≈0,8mol$
$\text{Theo pt :}$
$n_{H_2}=n_{Mg}=0,8mol$
$⇒V=V_{H_2}=0,8.22,4=17,92l$
$n_{HCl}=2.n_{Mg}=2.0,8=1,6mol$
$⇒C_{M_{HCl}}=\dfrac{1,6}{0,4}=4M$