AP Chemistry Unit 3.1 Study Set

Intramolecular Forces

Bond that occurs within the molecule

Intermolecular Forces

Attraction between two molecules

Which force is weaker, inter or intra?

Inter; however, inter is responsible for many different characteristics and every molecule will have inter forces

What are the types of intermolecular forces?

Ion-ion, ion dipole, dipole dipole, hydrogen bond, dipole-induced dipole, induced-dipole induced-dipole, London Dispersion

What is ion-dipole?

Ion and a polar molecule, strongest IMF, occurs when an ionic compound dissolves in water, ions are more attracted to the water than each other, ions and polar molecules stick together.

Ion-dipole force of attraction increases as…

The radius of the ion decreases, the charge of the on increases, the magnitude of the dipole on the polar molecule increases

Smaller ions, with a greater charge, in a polar solvent, have…

A higher attraction

What is dipole-dipole?

When polar molecules are near each other, 3rd strongest IMF, force of attraction increases as the magnitude of dipoles increases

When molecules are in constant motion, it is…

Hard for charges to stay aligned, causing positives to be with positives, vice versa, therefore causing the IMF to weaken, weaker since they’re between partial charges

When positive and negative dipoles line up well, the attractive forces are…

Maximized 

What do collisions do to IM/attractive forces?

Weaken them.

What are hydrogen bonds? 

Occurs between a hydrogen that is covalently bonded to F, O, or N, and another F, O, or N, with at least two lone pairs, 2nd strongest IMF, drawn with a dotted line

Why are hydrogen bonds so strong?

They’re very polar, smaller atom - highly concentrated, lone pairs increase partial negatives creating stronger attraction for the slightly positive hydrogen.

The more hydrogen bonds, the higher…

Boiling and melting point.

What is a dipole-induced dipole?

When a polar molecule gets close to a nonpolar molecule, doesn’t stay polarized, higher the polarity (or magnitude) = higher attraction

What is an induced-dipole induced-dipole? (London Dispersion)

The movement of electrons around the nucleus, everything has London Dispersion, because of the movement we get very tiny dipole moments, keeps plastics together, weakest IMF

The moreelectrons and larger the radius, the…

Lager the London dispersion force

More compact a molecule is, the more dipoles it has, which means the more…

London dispersion it has

The presence of pi bonds increase the…

Polarizability 

Electrons in pi bonds are more delocalized, so they can move…

More freely and assist in polarization. 

How do you find which compound has the highest melting point?

Step 1: Identify the intermolecular forces

Step 2: Look at which is bigger, bigger = higher melting point

The stronger the IMF, the…

Larger the atom is

The more hydrogen bonds there are, the higher the…

Boiling/melting point is

When do dipoles cancel out?

When the structure is similar, ex: nonpolar vs nonpolar

Dipole-dipole is…

Polar