Question

Polar molecules are the molecules :

• A. having a permanent electric dipole moment
• B. having zero dipole moment
• C. acquire a dipole moment only in the presence of electric field due to displacement of charges
• D. acquire a dipole moment only when magnetic field is absent

Answer 1

The Correct Option is A

In this question, we are required to determine which type of molecules are referred to as "polar molecules". Let's explore the concepts involved:

Polar Molecules: Polar molecules are molecules that have a permanent electric dipole moment. A dipole moment occurs when there is a separation of positive and negative charges within the molecule, which remains constant regardless of any external electric field. This typically happens when there is an unequal distribution of electrons between the atoms, leading to a partial positive charge on one end and a partial negative charge on the other.

Let's analyze each of the given options:

• Option 1: having a permanent electric dipole moment
  This definition matches exactly with what a polar molecule is. Such molecules always have a fixed dipole moment.
• Option 2: having zero dipole moment
  Molecules with zero dipole moment are known as non-polar molecules. Therefore, this option is incorrect.
• Option 3: acquire a dipole moment only in the presence of electric field due to displacement of charges
  This describes induced dipole moments which occur in non-polar molecules under the influence of an external electric field. Hence, this option is incorrect for defining polar molecules.
• Option 4: acquire a dipole moment only when magnetic field is absent
  This option does not accurately describe any recognized property of molecules regarding polar and non-polar characteristics, thus making it incorrect.

Conclusion: After evaluating all the options, it's clear that the correct answer is the first one: having a permanent electric dipole moment. This accurately defines polar molecules as they inherently possess a persistent dipole moment due to the permanent charge separation within their molecular structure.