Question

why the dipolemoment of BF3 is zero where the dipolemoment of NH3 is 1.49D?

Answer 1

Because in case of BF3 the net resultant force will cancel out but in case of NH3 the three forces will cancel each other but due to presence of loan pair net resultant force will not be zero.

Answer 2

Answer:

The dipole moment of BF3 is zero where the dipolemoment of

NH3 is 1.49D it is due to presence of lone pair in NH3. In BF3

there is symmetry and surrounding atoms are same i.e. F and

net dipole moment is zeo. The compound become non polar .

while due to presence of lone pair NH3 become polar and

have dipole moment .