Intermolecular Forces and Properties
Studied by 6 people
Learn
Practice Test
Spaced Repetition
Match
Flashcards1/171
There's no tags or description
Looks like no tags are added yet.
Name | Mastery | Learn | Test | Matching | Spaced |
|---|
No study sessions yet.
172 Terms
In TLC, increasing solvent polarity causes the product to run…
farther, which increases the Rf value
In TLC, decreasing solvent polarity causes the product to run…
a shorter distance, which decreases the Rf value
Molecular solids are held together by…
IMFs
Polarizability does not apply to…
charged species (ion-dipole, ions, etc)
In paper chromatography, if the mobile phase is polar, then polar components are more likely to travel…
farther
In paper chrom, lighter molecules tend to travel _________ than heavier molecules
farther
Under which temp and pressure conditions will a gas behave most ideally?
High temp and low pressure
How to determine which gas will behave the LEAST ideally
The molecules with the strongest IMFs will behave the least ideally (look for dipole-dipole, H bonds, etc)
Gases have the ability to condense because of their…
attractive forces
It’s easier for smaller gases to…
effuse and diffuse
Absolute temp is a measure of…
average kinetic energy
A higher molar mass for a gas will cause a _______ density
higher
Melting point and hardness of metallic solids…
varies
What elements are covalent networks usually composed of?
C, Si, Ge, B
What types of solids are brittle
ionic and covalent network
What is the strongest IMF?
ion-dipole (stronger than H bonds!!)
If you cool a gas, why might the actual volume be lower than what the ideal gas law predicts?
The ideal gas law assumes that gas particles do not experience interparticle attractions. As a real gas cools further, the intermolecular forces have greater effect as the average speed of the molecules decreases
Why might actual pressure be lower than what the ideal gas law predicts for a gas?
The gas has attractive IMFs that reduce the number of collisions against the container, decreasing pressure
Are molecular solids conductive?
NO!
Why are polar solutes more soluble in polar solvents?
They can form dipole-dipole IMFs which are stronger than LDFs alone
Why are longer hydrocarbons less soluble in water?
They have more nonpolar character
Less transmittance means more…
absorbance
Paper chrom is used to determine the number of…
components
Stronger IMFs result in an easier ability to…
condense (gas to liquid)
Why would a longer hydrocarbon gas be more likely to deviate from ideal behavior
A longer chain means it’s more polarizable and thus has stronger LDFs which defies the assumption of ideal behavior that gases don’t have IMFs
Total pressure is the sum of…
partial pressures
Covalent-network is _______ and has a higher _____ ____ than molecular solid structure
stronger; boiling/melting point
Molten ionic bonds contain freely moving ______ which conduct electricity
ions
If temp is constant, then what can’t change in a gas?
kinetic energy
Gases have relatively low…
densities
All gases can be…
easily compressed
Why are gases highly compressible?
Because they have large intermolecular spaces and thus weak IMFs
Coulomb’s Law can be applied to…
IMFs
In an ion-dipole IMF, a smaller ionic radius results in…
greater attraction
CH bonds are not highly ________ like OH bonds, thus they don’t create dipoles
polar
You can only use the gas constant 22.4L / 1 mol at…
STP (1 atm and 273K)
According to KMT, particles of a gas…
neither attract nor repel each other but collide
Hydrogens in hydrogen bonding have to be connected to a ________ to create a strong dipole and IMF
O, N, or F
Maxwell-Boltzmann distribution shows that at a specific temp, gas speeds…
vary across a spectrum
IMFs are always __________ than intramolecular forces
weaker
For gas stoichiometry, you have to use PV = nRT to find the volume or mass of a gas when…
you’re not at STP
Molar mass formula
Mass in grams / number of moles
Charles’ Law
V1/T1 = V2/T2
Boyle’s Law
P1V1 = P2V2
Avogadro’s Law
V1/n1 = V2/n2
Gay-Lussac’s Law
P1/T1 = P2/T2
Combined Gas Law
P1V1/T1 = P2V2/T2
1 atm = ___ mmHg
760
Ideal Gas Law
PV = nRT
Necessary units for gas laws
Liters
Kelvin
Moles
Gas constant for atm
0.0821
Kelvin formula
K = 273 + C
STP
273 K, 1 atm, 1 mol of gas = 22.4 L
Total pressure formula
PT = nT(RT/V)
Mole fraction formula
n1/nTotal
Partial pressure formula
P1 = X1PT
X = mole fraction
Gas density formula
D = PM/RT
M = molar mass
Gas molar mass formula
M = dRT/P
Van der Waals Forces
Everything besides ionic: LDF, dipole-dipole, hydrogen bonds
London dispersion forces (LDFs)
Occur for ALL substances with electrons, but are the only force acting on NONPOLAR particles
Temporary
Dipole-dipole forces
Occur when two POLAR molecules are attracted to each other
Permanent
Bulkier substances with larger surface area have stronger…
LDFs because the electron clouds are more polarizable
The strength of dipole-dipole forces is proportional to…
the charges of the dipoles involved
Hydrogen bonds
Special subset of dipole-dipole forces that involve polar molecules with H-F, H-O, or H-N
Involves molecules with large electronegativity differences which lead to dipoles with the largest partial charges
Strength of bond types ranked from weakest to strongest
LDF, dipole-dipole, hydrogen bond
Hydrogen bonds aren’t actually…
bonds, they’re IMFs between H atoms in one molecule and F, O, or N atoms in another
Molecules with hydrogen bonds have ____ IMFs
all 3
Van der Waals Forces only occur in…
neutral, covalently bonded molecules
Strong IMF: distance between molecules
small
Strong IMF: energy it takes to separate molecules
high
Strong IMF: affinity for other molecules like itself
high
Strong IMF: volatility
low
Strong IMF: boiling/melting point
high
Strong IMF: viscosity
high
Viscosity
resistance to flow
Weak IMF: distance between molecules
large
Weak IMF: energy to separate molecules
low
Weak IMF: affinity for other molecules like itself
low
Weak IMF: volatility
high
Volatility
how easily a substance will turn into a gas at room temp
Weak IMF: boiling/melting point
low
Weak IMF: viscosity
low
A stronger ionic bond can be determined by…
ion charges (larger the charge the stronger the bond)
When charges are equal, use ____ ______ to break ties when determining the strongest ionic bond
ion size (charge is still more important)
Smaller ionic radius =
greater attraction between the cation and anion because of Coulomb’s Law
Ion-dipole forces always require…
an ion and polar molecules
When ranking the IMF strength of molecules with only LDFs, the _________ molecules will have the strongest LDFs because they’re the most _________
largest; polarizable
Evaporation rate
how quickly it becomes a gas
Vapor pressure
the pressure exerted on a liquid by its gaseous state; how likely it becomes a gas (similar to volatility and evap rate); represents a partial pressure in total pressure of a system
Weak IMF: vapor pressure
high (more likely to become a gas and put pressure on the liquid)
Strong IMF: vapor pressure
low
Effect of increased temp on IMFs
decreases IMFs
Longer hydrocarbons have ______ LDFs because they have a greater ______ ______
stronger; surface area
Polarizable
How easily electron density is altered; larger atoms are more polarizable because the electrons can move more and are squishier; easier electron distortion which creates larger dipoles
How to go from a liquid to a gas
overcome IMFs
Why might a nonpolar substance still be stronger than a polar one?
The nonpolar substance likely has stronger LDF attraction due to a larger mass, enough so to overcome the dipole advantage
Properties of solids
Very strong interactions between particles
Definite shape and volume
Fixed arrangement of particles
1 degree of freedom: vibrational
Degrees of freedom
unique ways in which a particle can move (vibrations, rotations, and translations/moving in a line)
Liquid degrees of freedom
vibrations, rotations, and small translations
Gases degrees of freedom
vibrations, rotations, and translations (fullest extent)