Question

Which of the following compounds has a zero dipole moment?

• A. CH\(_2\)Cl\(_2\)
• B. NH\(_3\)
• C. CH\(_4\)
• D. PH\(_3\)

Hint:

Symmetrical molecules like CO\(_2\), CCl\(_4\), and BeF\(_2\) often have zero dipole moments.

Answer 1

The Correct Option is C

To determine which compound has a zero dipole moment, we need to consider the molecular geometry and the distribution of charge in each molecule. A zero dipole moment indicates that a molecule is non-polar, which typically arises from a symmetrical distribution of identical polar bonds that cancel each other out.

1. CH\(_2\)Cl\(_2\): The molecule has a tetrahedral shape, but the presence of two chlorine atoms and two hydrogen atoms leads to a net dipole moment. The difference in electronegativity between C-Cl and C-H bonds means that their dipoles do not cancel out, resulting in a non-zero dipole moment.
2. NH\(_3\): Ammonia has a trigonal pyramidal shape with a nitrogen atom having a lone pair. The N-H bonds are polar due to the difference in electronegativity between nitrogen and hydrogen. The dipole moment of NH\(_3\) is not zero.
3. CH\(_4\): Methane is a tetrahedral molecule, and the C-H bonds are symmetrically arranged. This symmetrical arrangement results in the cancellation of the dipole moments due to the equal bond polarities, leading to an overall dipole moment of zero.
4. PH\(_3\): Phosphine has a similar geometry to ammonia, with a lone pair on the phosphorus atom. However, the P-H bond is less polar than the N-H bond in ammonia, yet it still has a non-zero dipole moment due to its geometry and the presence of a lone pair.

Based on the analysis above, CH\(_4\) is the compound with a zero dipole moment because it is a symmetrical non-polar molecule where the individual bond polarities cancel each other out.