$\rm n_{H_2}=\dfrac{3,7185}{24,79}=0,15(mol)$

$\rm a.PTHH: Zn+2HCl \to ZnCl_2+H_2$

$\rm ZnO+2HCl \to ZnCl_2+H_2O$

$\rm b.n_{Zn}=n_{H_2}=0,15(mol)$

$\rm m_{Zn}=0,15.65=9,75(g)$
$\rm m_{ZnO}=17,85-9,75=8,1(g)$

$\rm \%Zn=\dfrac{9,75}{17,85}.100\%=54,6\%$

$\rm \%ZnO=100-54,6=45,4\%$

$\rm c.n_{ZnCl_2}=n_{ZnO}+n_{Zn}=\dfrac{8,1}{81}+0,15=0,25(mol)$

$\rm n_{HCl}=2n_{Zn}+2n_{ZnO}=2.0,15+2.0,1=0,5(mol)$

$\rm a=C_M HCl=\dfrac{0,5}{0,25}=2(M)$

$\rm m_{dd HCl}=0,8.250=200(g)$

$\rm m_{dd sau}=17,85+200-0,15.2=217,55(g)$

$\rm C\% ZnCl_2=\dfrac{0,25.136.100\%}{217,55}=12,5\%$

$\rm C_M ZnCl_2=\dfrac{0,25}{0,25}=1(M)$