Devaitions from Ideal Gas Behavior & InterMolecular Forces

what is Van der Vaals equation trying to say

attempts to describe the beahvior of real gases not ideal ones

Van der Vaals equation

(P + n²a/V²) * (V - nb) = nRT

a meaning in van der vaals equation

sticikiness correction factorLattractive forces between molecules reduce pressure. attractice forces between pairs of molescues increases as n/V²

b meaning in van der vaals equation

the volume of the container not filled by the gas

volume occupied by gas moleucle are not negligable.

volume ooccupied by gas molecules is in direct correlation with their sizes

predict when ideal gas

Small moleular mass and non polar = low a and b value (ex: He)

predict when non-ideal gas

high molecular mass and higher polarity (interaction between molecules) means higher a and b value

INTRAmolecular forces

any force WITHIN a molecule that hold atoms together

INTERmolecular forces

the attractive and repulsive forces that exist between molecules, influencing their physical properties like boiling point and melting point

what are the INTRAmolecular forces

ionic bond, covalent, metallic bond, polar covlane, nonpolar covalent

what are the INTERmolecular forces

Dipole-Dipole (D/D), hydrogen bonding, london dispersion attraction/dispersion forces, h bonding

permanent dipole

occur when two atoms in a molecule have substantially different electronegativity (EN (A) < EN (B))

Instantaneous dipole

temporary, fleeting separations of charge within a molecule or atom, arising from the random movement of electrons, leading to London dispersion forces

polarizability (aka distortion)

the ease with which the charge distribution is disorted

polarizability trend

the bigger the molecule the more dispersion forces

how does moleuclar shape influence magnitiude of dispersion forces

liner molecules increase dispersion forcs while spherical molescules have a smaller surface and decerease dispersion forces

dipole momeent

when two equal and opposite charges are separated by a distance, creating an electric dipole. 

for molecuels of approximately equal mass and size the strength of intermolecular atrractions increase with increaseing polarity

D/D forces increase with increasing moleuclar polairty and increasing sum of the changes in EN

important note for the D/D forces to increases

the moleucle needs to be POLAR and UNSYMETTTRICAL

when the temperature increases the molecules are

faster, harder to be organized, and D/D strength is less stablized

H bonding

a specific type of dipole-dipole attraction that occurs between a hydrogen atom bonded to a highly electronegative atom (H MUST BE POSITIVE)

what are the only only elements H can bond to be a H bond

O, F, or N. (MUST BE DIRECTLY ATTACHED TO H!!). essentially it is always between 2 electronegtive atoms

strength of h bond is based on:

change in EN and # of H bonds a molecule can make

# of H bonds a molecule can make

F= 1 O=2 N=3

ion dipole forces

an attractive force that results from the electrostatic attraction between an ion and a polar molecule

ion dipole forces exist between an ion and polar molecule

cations attracted to the negative end of a dipole and anions attracted to a positive end

the magnitidue of attraction increases as

ionic charge and dipole moment increases

remember this ranking for the smallest H-bonding molecules:

NH3 < HF < H2O

• NH3 has 3 H-bonds, but small ΔEN

• HF has largest ΔEN but only one H-bond

• H2O has sizeable ΔEN and two H-bonds

dispersion forces

Dominant in nonpolar molecules

• Increases with ↑MW

Dipole-Dipole

Dominant in polar molecules •

Increases with ↑∑ΔEN

Hydrogen Bonding

: increases N-H < O-H and with ↑# of H-bonds

Ionic

Dominant in salts and any compound with a full formal charge

Increases with ↑charge density

How does the MW of a molecule affect the IMF strength?

laeger MW means stronger IMF strength (directly propertional)