Which of the following is/are true? Select all that apply.
SF4 is a polar molecule and has a seesaw molecular geometry
The strongest intermolecular force in KBr(aq) is ion-dipole forces
BF3 is a nonpolar molecule and has a trigonal planar molecular geometry
CH3CHO is polar; there are dipole-dipole forces and dispersion forces between two CH3CHO molecules, but no hydrogen bonding
The correct answer and explanation is :
The correct statements are:
✅ SF₄ is a polar molecule and has a seesaw molecular geometry
✅ The strongest intermolecular force in KBr(aq) is ion-dipole forces
✅ BF₃ is a nonpolar molecule and has a trigonal planar molecular geometry
✅ CH₃CHO is polar; there are dipole-dipole forces and dispersion forces between two CH₃CHO molecules, but no hydrogen bonding
Explanation (≈300 words)
1. SF₄ (Sulfur Tetrafluoride):
SF₄ has 5 regions of electron density (4 bonding pairs and 1 lone pair) around the sulfur atom, based on VSEPR theory. This results in a seesaw molecular geometry. Due to the lone pair and the asymmetrical distribution of fluorine atoms, the dipole moments do not cancel, making SF₄ a polar molecule.
✅ True
2. KBr(aq):
KBr is an ionic compound that dissociates into K⁺ and Br⁻ ions in aqueous solution. Water is a polar solvent, and the interactions between the K⁺/Br⁻ ions and the partial charges on water molecules are called ion-dipole forces, which are stronger than hydrogen bonding or dipole-dipole interactions in this context.
✅ True
3. BF₃ (Boron Trifluoride):
BF₃ has three bonding pairs and no lone pairs on the central boron atom. This leads to a trigonal planar geometry, and because all three B–F bonds are identical and 120° apart, the molecule is symmetrical. Though each B–F bond is polar, the dipole moments cancel out, making BF₃ a nonpolar molecule.
✅ True
4. CH₃CHO (Acetaldehyde):
This molecule has a polar C=O group, making the entire molecule polar. It can engage in dipole-dipole and dispersion (London dispersion) forces. However, hydrogen bonding does not occur between CH₃CHO molecules because although the molecule has a hydrogen, it is not bonded directly to a highly electronegative atom like N, O, or F.
✅ True
Final Answer:
All statements are TRUE.