$\therefore \quad \text { millimole of acid }=0.24 \times 25$

$\Rightarrow \quad \text { mass of acid }=0.24 \times 25 \times 24.2\,mg$

$\text { for pure acid, }$

$\qquad V =\frac{ w }{ d } ;( d =1.21\,kg / L =1.21\,g / ml )$

$\therefore V =\frac{0.24 \times 25 \times 24.2}{1.12} \times 10^{-3}$

$=120 \times 10^{-3}\,ml$

$=12 \times 10^{-2}\,ml$