Question

29.2% (w/W) HCl stock solution has density of $1.25gm{L}^{-1}.$ The molecular weight of HCl is 36.5 g $mo{l}^{-1}.$The volume (mL) of stock ___

Answer 1

Mass of HCl in 1.0 mL stock solution = $1.25\times \frac{29.2}{100}=0.365g$
Mass of HCl required for 200 mL 0.4 M HCl = $\frac{200}{1000}\times 0.4\times 36.5=0.08\times 36.5g$
$\therefore$ 0.365 g of HCl is present in 1.0 mL stock solution.
$0.08\times 36.5gHCl$ will be present in $\frac{0.08\times 36.5}{0.365}=8.0mL$