The total number of neutrons present in 54 mL H₂O (l) are:

No. of moles of H₂O (l) $\left(\mathrm{l}\right)=\frac{54}{18}$
(d =1.0g,mLforH₂O)
H has no neutron
$\therefore$ number of neutrons in H₂O =3 x 8 x N_A