What volume of HCI solution of density 1.2 g/cm³ and containing 36.5010 by weight HCl, must be allowed to react with zinc (Zn) in order to liberate 4.0 g of hydrogen ?

$\mathrm{Zn}+2\mathrm{HCl}⟶{\mathrm{ZnCl}}_2+{\mathrm{H}}_2$
2 gms H₂ liberated by $2\times 36.5 \mathrm{gms} \mathrm{of} \mathrm{HCl}$

4 gms of H₂ liberated by  $-$ ?

$\frac{4\times 2\times 36.5}{2}=146 \mathrm{gms} \mathrm{of} \mathrm{HCl}$

given HCl is 36.5% by wt

In 100 gms of solution ,mass of HCl =36.5 gms

 146 gms of HCl would be obtained form $\frac{100\times 146}{36.5}$ =400 gms

Density =$\frac{\mathrm{mass}}{\mathrm{volume}}$

1.2 =$\frac{400}{\mathrm{x}}$

x =$\frac{400}{1.2}$ =333.333 cm³ or ml