Chemistry: Intermolecular Forces

interactions within a molecule

intramolecular forces

attractions between molecules and/or ions

• electrostatic

• weaker than intramolecular

• influence physical properties

intermolecular forces

separation of charge in an atom/molecule momentary uneven e- distribution

induced dipoles

intermolecular force between nonpolar molecules caused by presence of temporary dipoles in molecules

London dispersion forces (LDF)

increases strength when surface area, polarizability, or e- # increases
experienced by all atoms to some degree

LDF characteristics

relative ease of which an e- cloud can be distorted

polarizability

• way of interaction with other atoms

• over greater distances

induced dipole characteristic

between an ion and a molecule that has permanent dipole moment

ion dipole interaction

cluster of water molecules surrounding an ion in aqueous solution

sphere of hydration

between polar molecules (permanent dipoles)

dipole dipole interaction

between a polar molecule and opposite charge of induced dipole of another molecule

dipole induced dipole interaction

between hydrogen atom bonded to small, highly electronegative element (O, N, F)

hydrogen bond

strongest
ion-dipole
hydrogen bond
dipole-dipole
dipole-induced dipole
LDF
weakest

order of intermolecular forces strength

organic compound with general formula R-O-R'

ethers

"water fearing"

• repulsive interaction between solute and water

• non polar molecule

hydrophobic

"water loving"

• attractive interaction between solute and water

• polar molecule

hydrophilic

solubility down
temp up
pressure down

solubility of O2 in H2O

principle that concentration of sparingly soluble, unreactive gas in liquid is proportional to partial pressure of gas

Henry's law

Cgas = KH Pgas

Henry's law equation

1. temperature - T up VP up

2. surface area - SA up VP up

3. intermolecular forces - IMF up VP down

rate of vapor pressure factors

pressure exerted by a gas at a given temp in equilibrium with its liquid phase

vapor pressure

temperature at which the vapor pressure of a liquid equals 1 atm

normal boiling point

a relationship between the vapor pressure of a substance at two temps

Clausius-Clapeyron equation

graphical representation of how stabilities of physical states of a substance depend on temperature and pressure

phase diagram

temperature and pressure at which all three phases coexist

triple point

specific temperature and pressure at which liquid and gas phases have same density and are indistinguishable

critical point

hydrogen bonds

cause of unique characteristics of water

energy needed to separate molecules at surface of liquid

surface tension

concave/convex surface of a liquid in a tube with a small diameter

meniscus

cohesive

• hydrogen bonds between molecules adhesive

• liquid against glass

two forces of surface tension

rise of a liquid in a narrow tube as a result of adhesive forces within liquid

capillary action

resistance to flow of a liquid

• nonpolar - molar mass up viscosity up

• polar - LDF and dipole

viscosity