Thou Shalt Not Forget AP Chemistry - Unit 3

IMF’s from weakest to strongest:

London Dispersion, dipole-dipole, hydrogen bonding, ion-dipole

All molecules contain…

LD forces

LD forces get stronger as…

the molecule gets larger

Larger electron cloud =

more LD = more polarizable

All polar molecules contain…

dipole-dipole forces

dipole-dipole forces get strong…

as the molecule is more polar

Boiling point and melting point increase…

as IMF’s increase

Vapor pressure and volatility decrease…

as IMF’s increase

Molecular solids…

have low melting/boiling points and do not conduct electricity

When a molecular solid melts or boils…

the IMF”s between the molecules break, NOT the covalent bonds

SiO₂ and diamonds are…

covalent network solids and have very high boiling/melting points

Ionic solids have…

high melting/boiling points, and do not conduct electricity as a solid, but DO conduct when dissolved

Metallic “bonds” are…

between metals only, and always conduct electricity

Interstitial alloys are…

made when smaller atoms fit into the gaps between the larger atoms of a metallic crystal

Substitutional alloys are…

made when the radii of the metals are similar in size, substituted into the crystal lattice

Gas mixtures are…

homogenous because of the constant random motion of the particles

Gases are…

compressible because of the large spaces between the particles

Gas pressure is caused by…

collisions of particles with the walls of the container

More collisions =

More pressure

P and V are..

inversely related (P₁/V₁ = P₂/V₂)

T and V are..

directly related (T₁V₁ = T₂V₂)

T and P are..

directly related (T₁P₁ = T₂P₂)

Ideal gases obey..

all rules of the Kinetic Molecular Theory

Ideal Gas Law

PV=nRT

Temperature

Kelvin

Volume

Liters

Pressure

atm

One mole of an ideal gas

22.4 Liters ONLY at STP!!

Gas pressure and number of moles are 

directly related

Molar mass

dRT/P (“d” stands for density in units of g/L)

More molar mass a gas has

the slower it moves at a given temperature

Temperature

Average Kinetic Energy

Gases at the same temperature have

the same average kinetic energy

When collecting a gas by water displacement

P_total = P_{dry gas} + P_{water favor})

Real gases behave most like an ideal gas at 

high temperature and at low pressure

The more polar a gas is and the larger a gas is

the more it will deviate from ideal behavior

Small, nonpolar gases are

the most ideal

When filtering separate mixtures based on differences in particle size…

the large particles are trapped on the filter paper while the soluble component goes through the filter paper and stays in the “filtrate”

Distillation separates mixtures based on

differences in boiling point

boiling point depend on

the strength of IMF’s

Chromatography seperates

mixtures based on differences in polarity

Paper chromatograph

the component that is most similar in polarity to the “mobile phase” moves up the farthest

Like dissolves like

solubility in solvents of differing polarities

Beer’s Law

The darker the solution, the more it absorbs light

Absorbance is directly proportional to

concentration of solute

Hydrogen bonds are between a N/O/F in one compound

to a hydrogen that’s already bonded to a N/O/F in another compound