Intermolecular Forces flashcards

AP Chemistry

VB Theory

Orbitals will hybridize or blend together to create new orbitals so that a4 electrons will become unparied

sp hybridization

2 electron domains around the atom

sp² hybridization

3 electron domains around the atom

sp³ hybridization

4 electron domains around the atom

Single bonds are concidered what type?

sigma

Double bonds are considered what type?

Pi

Triple bonds are considered what type?

1 sigma, 2 pi

Molecular Orbital Theory

Electrons do not just hybridize to create new orbitals. They completely delocalize and spread across the entire molecule. Explains why some covalent compounds conduct electricity and why benzene is so stable.

Intermolecular forces are between what?

Bonds between molecules!

Ion-Dipole Force

Between Ions and Polar Compounds. The strongest IMF. If the charges are the same, then the smaller ions will result in a stronger attraction.

Coulomb’s law

higher charge results in shorter, stronger attraction

Hydration Sphere

Water molecules surround the ion. Opposite charges are facing eachother.

Dipole-Dipole Forces

Occurs between two polar covalent molecules. Heavier molecules form stronger forces.

Which is more polarizable. Heavier or lighter molecules?

Heavier!

London Dispersion Forces

Between two nonpolar covalent molecules or one polar and one nonpolar. Heavier molecules form stronger forces.

Longer Carbon Chains —>

More Polarizable.

Hydrogen Bonds

Between two molecules that both H-N, H-O or H-F. The more electronegative difference caused stronger IMFs. The more Hydrogen Bonds on a molecule cause the molecule to be stronger.

IMFs in order from weakest to strongest

London Forces, Dipole-Dipole, Hydrogen Bonding, Ion-Dipole.

Isomers

Same formula but have different chemical structures

Boiling Pressure

Stronger IMFs

Melting Points

Strong IMFs

Viscosity

Stronger IMFs

Hydration Energy

Negative with stronger IMFs

Vapor Pressure

Weak IMFs

Heats of states Changes

Strong IMFs → larger Delta H values

Heavier polar compounds have

Stronger IMFs than lighter polar compounds

Heavier Nonpolar compounds have

Stronger IMFs than lighter nonpolar compounds

A molecule with a longer carbon chain is

more polarizable

Melting is

endothermic

Freezing is

Exothermic

Volatile

Evaporates spontaneously

Non-volatile

Doesn’t evaporate spontaneously

Solution

Dissolved Salts

Homogeneous

Evenly Mixed

Steps to dissolve ionic solids in water

1. Break the crystal lattice (Endothermic)

2. Breaking the Hydrogen Bonds in H2O (Endothermic)

3. Form Hydragin Spheres (Exothermic)

Chromatography

Separation based on Polarity and molar mass. Chemicals most similar to the solvent in polarity would travel farthest.

Distillation

Separation based on strength of IMFs. Liquid with weakest IMFs boil off first.

Evaporation

Separation based on state. Liquids evaporate, dissolved solids do not

Filtration

Liquids and dissolved solids pass through filter paper, solids do not. Liquid that passes through is called the Filtrate. Solid bust be washed by distilled water. Solid is dried in an oven or desiccator.