Question

Assertion: $C{{H}_{3}}Cl$ is a polar molecule.
Reason: The Lewis diagram of polar molecules always has at least one lone pair of electrons.
(a) Assertion and reason are correct and reason is the correct explanation of assertion
(b) Assertion and reason are correct and reason is not the correct explanation of assertion
(c) Assertion is correct but reason is not correct.
(d) Assertion is not correct but reason is correct
(e) Both the assertion and reason are not correct.

Answer 1

Hint Polar molecules are those whose net dipole moment of the bond pairs do not cancel each other and have some net dipole moment and Lewis dot structure tells us about the number of valence electrons in an atom. Now you can easily answer the statement.

Complete answer:
First of let’s discuss what is a polar molecule. By the polar molecule , we mean that molecule in which there is separation of the charges i.e. the positive and the negative charges and the molecule have net dipole. On the basis of the bonds which show the net dipole in a molecule, we can check whether the given molecule is polar or nonpolar.
On the other hand, the Lewis dot diagram tells us about the number of the valence electrons present in an atom and helps to know whether the valence electrons exist as lone pairs of electrons or are present in the bond pair.
Now considering the statement as;
Assertion: In the methyl chloride, all the atoms i.e. carbon, hydrogen and chlorine have different electronegativities and have symmetrical structure and the bond dipoles do not cancel each other.
So, methyl chloride is a polar molecule and thus, the assertion is correct.
Reason: As discussed above, the Lewis dot is the structural representation of the valence electrons and it is not essential that the polar molecules should have at least one lone pair of electrons.

So, thus, the reason is incorrect.

Hence, option (c) i.e. assertion is correct but reason is not correct is the correct answer.

Note: The polarity of the molecule depends on the presence of the electronegative atom in the molecule. More the electronegativity of the atom, more is the tendency of the atom to attract the shared pair of electrons towards itself and more is the polarity of the molecule and vice-versa.