Question

Each of the following options contains a set of four molecules, identify the option(s) where all four molecules possess permanent dipole moment at room temperature.
This question has multiple correct options
(A) $N{{O}_{2,}}N{{H}_{3}},POC{{l}_{3}},C{{H}_{3}}Cl$
(B) $B{{F}_{3}},{{O}_{3}},S{{F}_{6}},Xe{{F}_{6}}$
(C) $BeC{{l}_{2}},C{{O}_{2}},BC{{l}_{3}}_{,}CHC{{l}_{3}}$
(D) $S{{O}_{2}},{{C}_{6}}{{H}_{5}}Cl,{{H}_{2}}Se,Br{{F}_{5}}$

Answer 1

Hint: Dipole moments occur when there is a separation of charge and it is a measure of the polarity of the molecule. Among the given molecules $BeC{{l}_{2}},C{{O}_{2}},BC{{l}_{3}},S{{F}_{6}}$and $B{{F}_{3}}$ are non-polar which means that they do not have permanent dipole moment.

Complete step by step solution:
- As we know, polar character is the separation of negative and positive charges in a compound and the measurement of this polar character of a chemical bond in a molecule or between two atoms is given by dipole moment.
- In any system the separation of charges will lead to the formation of dipole moment and the main reason for the development of dipole moment is the differences in electronegativity between the chemically bonded atoms.
- Although the net charge on a molecule is zero, the nature of chemical bonds is such that the negative and positive charges do not totally overlap in most molecules and such molecules are said to be polar because they possess a permanent dipole moment($\mu $).

- As we can see all the molecules have nonzero dipole moment and hence they possess permanent dipole moment. Hence option (A) is correct.

- The net dipole moment of the molecules$B{{F}_{3}}$ and $S{{F}_{6}}$ is zero and hence they do not possess permanent dipole moments. Hence option (B) is incorrect.

-Only the molecule $CHC{{l}_{3}}$ has permanent dipole moment. Hence option (C) is also incorrect.

As we can see all the molecules have nonzero dipole moment and hence they possess permanent dipole moment. Hence option (D) is correct.
Thus the set of molecules $N{{O}_{2,}}N{{H}_{3}},POC{{l}_{3}},C{{H}_{3}}Cl$ and $S{{O}_{2}},{{C}_{6}}{{H}_{5}}Cl,{{H}_{2}}Se,Br{{F}_{5}}$ possess permanent dipole moment at room temperature.

Therefore the answers are options (A) and (D).

Note: The difference between the terms bond dipole moment and total dipole moment should be noted. The total dipole moment in a polyatomic molecule is the vector sum of all the bond dipoles whereas the bond dipole moment is the dipole moment between the single bonds of a diatomic molecule.