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Which of the following molecules has a permanent electric dipole moment, even in the absence of an electric field?

Asked in GSEB Board July 2021 · Dipole moment and dipole field

Answer: (1) H₂O

Step-by-step solution

Idea: a molecule has a permanent dipole moment when its centre of positive charge and its centre of negative charge do not coincide.

H₂O is bent (bond angle about 104.5°), so its two O-H bond dipoles do not cancel: the molecule is polar.

CO₂ (linear) and CH₄ (tetrahedral) are symmetric, so their bond dipoles cancel; O₂ has no charge separation to begin with.

So of these, only H₂O has a permanent dipole moment.

Why the other options are wrong

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