Describe the intermolecular forces that are present in each...

Describe the intermolecular forces that are present in each of the following compounds. Which kind of force would have the greatest influence on the properties of each compound? (a) ethyl alcohol, $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ (contains one $\mathrm{C}-\mathrm{O}$ single bond); (b) phosphine, $\mathrm{PH}_{3} ;$ (c) sulfur hexafluoride, $\mathrm{SF}_{6}$.

Key Concepts

London Dispersion Forces

Also known as induced dipole-induced dipole interactions, these are the weakest intermolecular forces and exist in all molecules, whether polar or nonpolar. They arise from temporary fluctuations in electron density that create instantaneous dipoles, and although individually weak, they can become significant in larger or more polarizable molecules.

Molecular Geometry and Polarity

The overall shape or geometry of a molecule determines whether individual bond dipoles cancel out or add up to produce a net dipole moment. Molecular geometry is crucial in predicting the presence and strength of intermolecular forces because symmetrical arrangements often lead to nonpolar molecules, relying mostly on London dispersion forces, while asymmetrical arrangements in polar molecules can facilitate dipole-dipole interactions or hydrogen bonding.

Hydrogen Bonding

Hydrogen bonding is a strong type of intermolecular force that occurs when hydrogen is covalently bonded to highly electronegative atoms such as oxygen, nitrogen, or fluorine. This bond creates a significant partial positive charge on the hydrogen, which can then interact strongly with lone pairs on electronegative atoms in neighboring molecules, greatly influencing the compound's physical properties like boiling point and solubility.

Dipole-Dipole Interactions

These are forces between molecules that possess a permanent dipole moment due to unequal sharing of electrons in polar bonds. The positive end of one polar molecule attracts the negative end of another, which affects properties like melting and boiling points. Their strength depends on the magnitude of the molecular dipoles.

Transcript

Please give Ace some feedback