Question

Dipole moment of BF3 and NH3

Answer 1

In tetra-atomic molecules such as BF3 and NH3, the dipole moment of BF3 molecule is zero while that of NH3 is 1.49 D.

In BF3 molecule,

BF3 has symmetrical structure in which the three B-F bonds are oriented at an angle of 120° to one another.

Each BF bond has a dipole moment with a partial negative charge on the fluorine (it is much more electronegative than the boron).

Also the three bonds lie in one plane and the dipole moments of these bonds cancel one another giving net dipole moment equal to zero.

Thus, the shape of the molecule (trigonal planar) is such that the bond dipole moments add up to zero.

In NH3 molecule,

NH3 has a pyramidal structure.

The individual dipole moments of three N-H bonds give the resultant dipole moment as 1.49 D.

Thus, the presence of polar bonds in a polyatomic molecule does not mean that the molecules are polar.

Answer 2

hey mate..

here is your answer...

In tetra-atomic molecules such as BF3 and NH3, the dipole moment of BF3 molecule is zero while that of NH3 is 1.49 D.

In BF3 molecule,

BF3 has symmetrical structure in which the three B-F bonds are oriented at an angle of 120° to one another.

Each BF bond has a dipole moment with a partial negative charge on the fluorine (it is much more electronegative than the boron).

Also the three bonds lie in one plane and the dipole moments of these bonds cancel one another giving net dipole moment equal to zero.

Thus, the shape of the molecule (trigonal planar) is such that the bond dipole moments add up to zero.

In NH3 molecule,

NH3 has a pyramidal structure.

The individual dipole moments of three N-H bonds give the resultant dipole moment as 1.49 D.

Thus, the presence of polar bonds in a polyatomic molecule does not mean that the molecules are polar.

hope it helps...