Question

1- the dipole moments of the given molecules (BF3, NF3 & NH3) are such that :
A-BF3>NF3>NH3
B-NF3>BF3>NH3
C-NH3>NF3>BF3
D-NH3>BF3>NF3
E-NH3=BF3=NF3

What is dipole . And how to determine this moment . Solution with explantion . Quick .. :)

Answer 1

Dipole moment is the product of charge and distance between the charges. It is a vector quantity therefore we should follow vector addition.
I have drawn the structures of the three compounds along with directions of dipole moment.
In NH3 all the moments assist each other so net moment adds up.
In NF3 moment of lone pairs is opposite to that of N - F. So net dipole moment reduces.
In BF3 the molecule being planar and the directions being away from central molecule, the moments cancel each other. Thus net moment is 0.
Hence the order becomes NH3 than NF3 than BF3

Answer 2

$NH_3>NF_3>BF_3$ (Option C)

• Dipole: A pair of equal and opposite charge particles separated by a small distance.
• Dipole moment is determined by looking at their charge separation distance. When an atom has more electronegativity it consists of more dipole moment.
• The formula to find dipole moment is, p = qd where 'q' is the charge and 'd' is the smallest distance.
• The correct answer is option C because they are arranged in the decreasing order of their electronegativity which implies $NH_3$ has more dipole moment compared to $BF_3$.