AP Chem - Unit 3a

Intramolecular forces

interaction within a single molecule that hold atoms together

Intermolecular forces

interaction between two molecules that are coulombic

what factor does and does not change distribution of the graph

Pressure doesnt, mass and temp do

Dipole-Dipole

Any IMF between two polar molecules that can be attractive or repulsive. Orientation matters because opposite poles need to be next to eachother. Strength of IMF is directly related to the strength of dipole

Dipole-Induced Dipole

IMF between one polar and one non-polar molecule. The dipole of one polar molecule approaches a non-polar molecule, and the electrons on the non-polar molecule are repelled by the negative part of the polar molecule, causing a temporary dipole

London Dispersion forces

IMF between two nonpolar. Electrons move randomly around an atom.

• They shift to one side by chance.

• A temporary dipole forms.

• This forces a neighbor to shift too.

• The opposite charges attract briefly.

• Electrons keep moving, and the cycle repeats.

the larger the electron cloud (bigger molecule)

the more polarizable, the greater strenth of LDF (elongated)

Hydrogen Bonding

when N, O, or F is bonded with H within a molecule and then attracted to a LONE PAIR N, O, or F of another molecule.

Ion Dipole interaction

The magnetic-like attraction between a ions and a polar molecule.

• How it works:

  • Positive ions stick to the negative side of the molecule.

  • Negative ions stick to the positive side of the molecule.

• MAKES SOLUBILITY

hierarchy of strength

ion-dipole, h bonding, dipole-dipole, dipole-induced dipole, ldfs

Vapor Pressure

the pressure created by gas particles (vapor) above a liquid in a closed container.

Dynamic equilibirum

the rates of evaporation and condensation become equal. the amount of vapor above the liquid stays relatively constant

as temperature increases, vapor pressure

increases because they move faster and have more energy to evaporate

as IMFs increase what about vapor pressure

vapor pressure decreases because its harder for them to escape

boiling point increase when

imfs increase, vapor pressure at a given temp decrease

viscosity

resistance to flow (increases as imfs increase)

volatile

a substance has a high tendency to turn into a gas or vapor at normal temperatures and pressure. have high vapor pressure. decreases as imfs increase

larger molecules have

stronger imfs

covalent network solids

• Carbon allotropes: Diamond and Graphite (C).

• Silicon compounds: Quartz/Sand (SiO₂) and Silicon Carbide (SiC).

• Pure metalloids: Pure Silicon (Si) and Germanium (Ge).

• Boron compounds: Boron Nitride (BN).

Phase of matter is dictated by

kinetic energy, pressure and temp of surronding enviornemnt

Solids degree of freedom

vibrational which means they cant move past each other. In fixed position with higher density

Kinetic energy of liquids

in the middle, bc its faster than solids slower than gases. Vibrational and translation degree of freedom

when does a liquid boil

when vapor pressure = barometric pressure

only state of matter that is compressible

gas

Kelvin Conversion

Celcius + 273.15

pressure and volume

inversely proportional P1V1=P2V2

volume and number of moles

directly proportional v1/n1 = v2/n2

Avagadro’s Laws

equal volumes of gases with constant temp and pressure contain the same number of particles. 1 mol =22.3 L at STP. v1/n1 = v2/n2

pressure and number of particles relationship

n1/p1 = n2/p2

volume and temp (kinetic energy)

v1/t1=v2/t2

pressure and temperature

t1/p1 = t2/p2

temperature second meaning

the kinetic energy of a particle, faster particles create a higher collision frequency and a collision with more force

combined gas law

p1 v1. = p2 v2

_____……._____

t1 t2

partial pressure and mole fraction

N i. = Pi

_________

n total ptotal

density within the gas law instead of moles

P (MM) = dRT

solving for density (has to be grams per liter)

d = PM/RT

Assumptions under the ideal gas law

• constant motion

• Between collisions, particles have constant velocity and direction

• (elastic) when particles collide with the wall, their new velocity is the same as before

• Particle size is negligible

• constant K.E

effusion

the passage of gas particles through tiny holes of the container. higher speeds increase effusion and large mass descreases

diffusion

rate at which a gas mixes with other gases when a container is open. so larger mass means slower and higher velocity means faster

what proves that real gases have imfs

all gases can condense into liquids

why do gases condense to form liquids

gas particles lose enough kinetic energy that intermolecular forces can pull them closer together.

IMFs cause what about pressure

less pressure than an ideal gas

real volume of particles

causes increase in pressure bc the particles have les free space to move so they collide with the wall more

ideal conditions

high temp, low pressure