$n_{H_2}=2,24/22,4=0,1mol$
$a.Zn+2HCl\to ZnCl_2+H_2↑$
$\text{Cu không phản ứng với HCl}$
$\text{b.Theo pt :}$
$n_{Zn}=n_{H_2}=0,1mol$
$⇒m_{Zn}=0,1.65=6,5g$
$⇒m_{Cu}=10-6,5=3,5g$
$\text{c.Theo pt :}$
$n_{HCl}=2.n_{H_2}=2.0,1=0,2mol$
$⇒C_{M_{HCl}}=\dfrac{0,2}{0,2}=1M$