a,
$Zn+2HCl\to ZnCl_2+H_2$
b,
$n_{Zn}=\dfrac{6,5}{65}=0,1\ (mol)$
$\Rightarrow n_{HCl}=2n_{Zn}=2.0,1=0,2\ (mol)$
$\Rightarrow C_{M_{dd\ HCl}}=\dfrac{0,2}{0,1}=2\ (M)$
c,
$n_{H_2}=n_{Zn}=0,1\ (mol)$
$\Rightarrow V_{H_2}=0,1.22,4=2,24\ (l)$
d,
$FeO+H_2\xrightarrow{t^o} Fe+H_2O$
$\Rightarrow n_{Fe}=n_{H_2}=0,1\ (mol)$
$\Rightarrow m_{Fe}=0,1.56=5,6\ (g)$