DIPOLE MOMENT

            The quantitative measurement of degree of polarity is called dipole moment. OR

¥          The product of the magnitude of the charge (positive or negative) and the distance between them is called dipole moment

             μ = q x r here μ (mu) is dipole moment while q and r are charge and bond length..

¥          It is a vector quantity and the direction is from positive to negative end.

¥          it is represented by an arrow with cross tail.

¥          A molecule with the positive charge at one end and negative at the other end is called           dipole

¥          unit of dipole moment is Debye. 1D= 1x 10^-18 esu x cm

            In SI system it is equal to 3.36 X 10^-30 C.m

           

Measurment;

            The instrument used for the measurement of dipole moment is electric condenser.It is a        connected to a battery of known voltage. When polar molecule is placed is place in the        condenser , the polar molecule aligned themselves in such a way that the positive end of       molecule come towards negative plate and negative end toward positive plate. The decrease in electric field is observed. From that decrease in electric field the dipole         moment is observed

APPLICATION or IMPORTANCE

            Dipole moment tells us

1;         Percentage Ionic characters of bond;

            From experimentally determined dipole moment the percentage of ionic character of            bond    can be calculated as

            Percentage ionic character=      D.M (observed) exp       X100                                                                                                                                              D.M (ionic) theo

2;         GEOMETRY OF MOLECULE;

Those molecules which has more than one possible geometry, Its geometry can be predicted by knowing the value of dipole moment.

For poly atomic hetronuclear molecules the dipole moment is the vector sum of all the         individual bond moment

A; The dipole moment of SO₂ is 1.62 D which shows its bent shape.

B; The dipole moment of BF₃ is zero; It means that all angle is of the same value. And its    shape will be trigonal planer.

C;        the dipole moment of water is 1.84, which indicate that its geometry is not linear.      But is angular

D;        dipole moment of CO₂ is zero, which indicate its linear geometry.

3;         Identification of cis/Trans isomers can be determined.

            The dipole moment of Tran’s isomer is zero.