Question

Which one of the following molecules has a dipole moment?

• A. CS₂
• B. CO₂
• C. CH₄
• D. CHCl₃

Answer 1

The Correct Option is D

To determine which molecule has a dipole moment, we need to consider the molecular geometry and the difference in electronegativity between the atoms in each molecule. A dipole moment arises when there is an uneven distribution of electron density, typically due to differences in electronegativity, resulting in a polar molecule.

1. Let's analyze each of the given molecules:
   • CS₂: Carbon disulfide is a linear molecule. The electronegativity difference between carbon and sulfur leads to dipoles pointing towards the sulfur atoms. However, due to its linear shape, the dipoles are symmetrical and cancel each other out. Therefore, CS₂ has no dipole moment.
   • CO₂: Carbon dioxide is also linear. The dipoles between carbon and oxygen are equal and opposite, canceling each other out, so CO₂ has no dipole moment.
   • CH₄: Methane is a tetrahedral molecule. The C-H bonds have very small polarity, and due to the symmetry of the tetrahedral shape, any small dipoles cancel out, resulting in no overall dipole moment.
   • CHCl₃ (Chloroform): This molecule has a tetrahedral geometry but is not symmetrical due to the presence of three chlorine atoms, which are more electronegative than hydrogen. The electronegativity differences create dipoles pointing towards the chlorine atoms. This imbalance results in a net dipole moment for the molecule.
2. From the above analysis, CHCl₃ is the only molecule with a net dipole moment because of its asymmetric shape and the presence of polar bonds that do not cancel out.

Therefore, the correct answer is CHCl₃, which has a dipole moment due to its molecular geometry and difference in electronegativity among its atoms.