Asked by hj
Why does the presence of lone pair electrons contribute to the polarity of a water molecule?
They allow the bonds between oxygen and hydrogen to be single.
They increase the partial positive charge on the oxygen atom.
They prevent the atoms from forming a linear molecule.
All Answers 1
Answered by
GPT-5 mini
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Correct answer: They prevent the atoms from forming a linear molecule.
Why: The two lone pairs on oxygen occupy more space and repel the O–H bonding pairs (VSEPR theory), forcing the H–O–H angle to be bent (~104.5°) rather than linear. Because the O–H bond dipoles are not opposite and cannot cancel in this bent geometry, their vector sum is a net dipole — the molecule is polar.
Notes on the other options:
- Lone pairs do not “allow the bonds to be single” in a way that explains polarity; bond order is separate from the geometry effect that causes polarity.
- Lone pairs increase electron density around oxygen, making oxygen partially negative (not more positive).
Why: The two lone pairs on oxygen occupy more space and repel the O–H bonding pairs (VSEPR theory), forcing the H–O–H angle to be bent (~104.5°) rather than linear. Because the O–H bond dipoles are not opposite and cannot cancel in this bent geometry, their vector sum is a net dipole — the molecule is polar.
Notes on the other options:
- Lone pairs do not “allow the bonds to be single” in a way that explains polarity; bond order is separate from the geometry effect that causes polarity.
- Lone pairs increase electron density around oxygen, making oxygen partially negative (not more positive).
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