Question:medium

Which one of the following molecules is nonpolar?

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Linear molecules with identical terminal atoms (CO\(_2\), BeCl\(_2\), C\(_2\)H\(_2\)) are nonpolar. Bent molecules (H\(_2\)O, SO\(_2\)) are polar.
Updated On: May 10, 2026
  • CO\(_2\)
  • H\(_2\)O
  • CH\(_3\)OH
  • HCl
  • NaCl
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The Correct Option is A

Solution and Explanation

Step 1: Understanding the Concept:
A molecule is considered nonpolar if it has a net dipole moment of zero. This can occur in two ways: either all the bonds in the molecule are nonpolar, or the molecule has polar bonds but its symmetrical geometry causes the individual bond dipoles to cancel each other out.
Step 3: Detailed Explanation:
Let's analyze each molecule:
(A) CO\(_2\) (Carbon Dioxide):
The molecule has a linear structure: O=C=O.
Oxygen is more electronegative than carbon, so each C=O bond is polar, with the dipole moment pointing from C to O.
However, the two bond dipoles are equal in magnitude and point in exactly opposite directions. As a result, they cancel each other out, and the net dipole moment of the molecule is zero. Thus, CO\(_2\) is a nonpolar molecule.
(B) H\(_2\)O (Water):
The molecule has a bent (V-shaped) structure due to the two lone pairs on the oxygen atom.
The O-H bonds are polar because oxygen is highly electronegative. The bond dipoles point from H to O.
Because of the bent geometry, the two bond dipoles do not cancel out. They add up vectorially to give a significant net dipole moment. Thus, H\(_2\)O is a polar molecule.
(C) CH\(_3\)OH (Methanol):
This molecule has a tetrahedral geometry around the carbon and a bent geometry around the oxygen. It is asymmetrical.
It contains polar C-O and O-H bonds. Due to the lack of symmetry, these bond dipoles do not cancel, resulting in a net dipole moment. Thus, Methanol is a polar molecule.
(D) HCl (Hydrogen Chloride):
This is a simple diatomic molecule. Chlorine is more electronegative than hydrogen, creating a polar covalent bond. Since there is only one bond, there is a net dipole moment. Thus, HCl is a polar molecule.
(E) NaCl (Sodium Chloride):
This is an ionic compound, formed by the complete transfer of an electron from Na to Cl, creating Na\(^+\) and Cl\(^-\) ions. The electrostatic attraction between these ions results in a very large dipole moment. It is extremely polar.
Step 4: Final Answer:
Based on the analysis, CO\(_2\) is the only nonpolar molecule among the given options because of its linear symmetry. This corresponds to option (A).
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