Question

Estimate the dipole moment of an HF molecule from the electronegativities of the elements and express the answer in Debye and Coulomb∙meters.

Answer 1

Dipole moments occur when there is a separation of charge. They can occur between two ions in an ionic bond or between atoms in a covalent bond; dipole moments arise from differences in electronegativity. The larger the difference in electronegativity, the larger the dipole moment. The distance between the charge separation is also a deciding factor in the size of the dipole moment. The dipole moment is a measure of the polarity of the molecule.

the electronegativity of a Hydrogen atom is 2.2 and that of Fluorine is 3.98 thus the difference in their electronegativities is 1.78

Taking the bond length of HF to be 0.92 A^o we have 1 e charge having distance of 0.92 between them.

using formula

where, = dipole moment

Q = charge separated

and R = distance between the charges

since HF is H ⁺ and F^- i.e. 1e charge separated with 0.92 * 10^-10 m