A neutral water molecule (H20) in its vapour state has an electric dipole moment of magnitude 6.4 × 10-30 C-m. How far apart are the molecules' centres of positive andnegative charge?

There are 10 electrons and 10 protons in a neutral water molecule.So, its dipole moment isp = q (21) = 10 e (21)Hence, length of the dipole, i.e., distance between centres of positive and negative charges is2l=p10e=6.4×10-3010×1.6×10-19=4×10-12 m=4pm