VSEPR & Hybridization (College Board AP® Chemistry): Exam Questions

Sulfur tetrafluoride (SF₄) is a covalent molecule that contains a central sulfur atom bonded to four fluorine atoms.

Draw the Lewis diagram of SF₄, showing all valence electrons.

i) State the molecular shape of SF₄.

ii) Explain how the number of bonding and non-bonding electron pairs around sulfur determines this shape.

Predict whether SF₄ has bond angles exactly equal to 120° and 90°, and explain your answer.

A researcher is investigating the structure and properties of acetate ion (CH₃COO⁻), phosphorus pentachloride (PCl₅), and xenon tetrafluoride (XeF₄). These substances demonstrate key bonding patterns and structural effects on physical properties.

Draw two valid resonance structures of the acetate ion, CH₃COO⁻, and explain how resonance affects the bond lengths in the ion.

Determine the hybridization of each carbon atom in the acetate ion. Justify your answer based on electron domains.

Predict the molecular geometry of phosphorus pentachloride (PCl₅) and explain why axial and equatorial bonds experience different repulsions.

i) Predict the molecular geometry of xenon tetrafluoride (XeF₄). Justify your answer based on electron domain geometry.

ii) Explain why XeF₄ has no overall dipole moment.

Compare the polarity of CH₃COOH (acetic acid) and CH₃COO⁻ (acetate ion), and explain how their molecular structures contribute to their relative polarity.

Formaldehyde (CH₂O) is an important industrial compound commonly used as a preservative and in polymer production.

Determine the molecular geometry of formaldehyde (CH₂O). Justify your answer.

Identify the number of sigma and pi bonds in formaldehyde.

Explain how the hybridization of the central carbon atom in formaldehyde influences the polarity of the molecule.

Dimethyl ether (CH₃OCH₃) and ethanol (CH₃CH₂OH) have the same molecular formula (C₂H₆O) but exhibit different physical properties, such as boiling points.

Determine the hybridization of the oxygen atom in both dimethyl ether and ethanol.

Predict the molecular geometry around the oxygen atom in both molecules.

Explain why ethanol has a significantly higher boiling point than dimethyl ether, despite having the same molecular formula.

Phosphorus trifluoride (PF₃) and boron trifluoride (BF₃) are both trifluoride compounds, yet they have different molecular geometries and polarities.

Determine the hybridization of the central atom in PF₃ and BF₃.

Compare the bond angles in PF₃ and BF₃.

Explain why they are different.

Predict whether each molecule is polar or nonpolar. Justify your answer.