The radius of water molecule having density 1g mL^-1 is

.Volume of 1gm water molecules= 1cm³

Volume of 181​ mole of water= 10⁻⁶m³

181​ mole of water= 6.023×1023×181​ molecules of water

Volume of 181​×6.023×1023 molecules= 10⁻⁶m³

Hence, Volume of one water molecule= 0.2988×10⁻²⁸m³

Let. the radius of water molecule be r

0.2988×10⁻²⁸=34​×π×r³

⇒ r=0.1925 nm=1.925A˚