Question

Which of the statements is false in the case of polar molecules?

• A. Centers of positive and negative charges are separated in the absence of external electric field.
• B. Centers of positive and negative charges are separated in the presence of external electric field.
• C. Do not possess permanent dipole moments.
• D. Ionic molecule HCl is the example of polar molecule.

Answer 1

The Correct Option is C

Let's examine each statement about polar molecules to identify the false one:

(A) Centers of positive and negative charges are separated in the absence of external electric field. This is true. Polar molecules have a permanent dipole moment due to differences in electronegativity between the atoms. This means the centers of positive and negative charges are inherently separated even without an external field.

(B) Centers of positive and negative charges are separated in the presence of external electric field. This is true. An external electric field will further polarize the molecule, increasing the charge separation. Even nonpolar molecules experience some charge separation in an external field (induced dipole).

(C) Do not possess permanent dipole moments. This is false. This statement is the opposite of the definition of a polar molecule. Polar molecules, by definition, do possess permanent dipole moments.

(D) Ionic molecule HCl is the example of polar molecule. This is true. HCl is a classic example of a polar molecule due to the significant electronegativity difference between hydrogen and chlorine. Though often confused, ionic bonds have much larger electronegativity differences than polar bonds.

The correct answer is (C) Do not possess permanent dipole moments.

Answer 2

Understanding Polar Molecules: Polar molecules are molecules where there is an uneven distribution of electron density, resulting in a molecule having a slightly positive end and a slightly negative end. This uneven distribution arises due to differences in electronegativity between the atoms in the molecule. This leads to a permanent dipole moment in the molecule, even in the absence of an external electric field.

Let's analyze each statement:

(A) Centers of positive and negative charges are separated in the absence of external electric field.
This statement is true. This is the defining characteristic of a polar molecule. The separation of charge centers is inherent to the molecular structure and does not require an external field.

(B) Centers of positive and negative charges are separated in the presence of external electric field.
This statement is also true. An external electric field will influence the orientation and alignment of the existing dipoles in polar molecules, and the separation of charges will still be present and might be slightly affected but fundamentally remain separated.

(C) Do not possess permanent dipole moments.
This statement is false. Polar molecules are *defined* by the presence of permanent dipole moments. This is the key difference between polar and non-polar molecules.

(D) Ionic molecule HCl is the example of polar molecule.
This statement is true. Hydrogen chloride (HCl) is a classic example of a polar molecule. Chlorine is much more electronegative than Hydrogen, leading to a polar covalent bond and a significant dipole moment. While HCl can also be considered to have ionic character due to the significant electronegativity difference, it is predominantly considered a polar covalent molecule and a good example of a polar molecule.

Therefore, the false statement is (C).