Unit 3 Flashcards
Three types of Intermolecular Forces
- Dipole-Dipole
- H Bonds
- London Dispersion
What are dipole dipole bonds and its properties?
polar molecule attraction
melts and boils at low temps due to weak attraction - gases and liquids at room temps
What are H bonds and what are its properties?
When H gives up its e-, it has a + charge
High boil and melt temps due to STRONG attraction
(liquids)
Why are H bonds the strongest?
There is no electron shielding so the attraction is much much stronger
What are London Dispersion Forces
Depends on random motion of e-: higher number of e- = higher attraction =
higher melting and boiling points
(gases)
What is the weakest IMF?
London Dispersion Forces due to the randomness
What kind of molecule does not experience IMFs?
Ionic Molecules and they are SOLIDS at room temp
What happens to Ionic bonds when they change phases?
bonds are broken
What happens to covalent bonds when they change phases?
bonds are NOT broken
What are the melting point <> stuff
network covalent > ionic > metallic > covalent
Vapor Pressure
molecules are in constant motion.
If they hit hard enough, they can escape from their IMF
if temperature rises, vapor pressure…
increases
if there are stronger IMF, vapor pressure
is weaker
What is the rule for dissolving?
Like dissolves like
polar dissolves polar
Electrolytes
the ions dissolved from ionic bonds, which are great for electric conductivity
What does distillation do?
Takes advantage of different boiling points to separate mixtures of substances.
What does a Maxwell Boltzmann diagram tell me?
Demonstrates the range of velocities for the molecules of gas.
If temperature rises, Kinetic Energy…
increases
Effusion
rate of gas diffusing through microscopic holes
If temperature rises, rate of effusion…
increases
If mass of the individual gas is bigger, rate of effusion…
decreases
Ideal Gas Equation
PV = nRT
Combined Gas Law
(P1V1)/T1 = (P2V2)/T2
Boyle’s Law
P1V1 = P2V2
Charles’s law
V1/T1 = V2/T2
What does Dalton’s law state?
Mixture of gases’ pressure is the sum of the individual gases’ pressure in the mixture
Calculation of Partial Pressure
(partial pressure) = (Total pressure) x (percentage of gas in total)
When do deviations from Ideal Behavior occur?
- Low temperatures
- High Pressures
Volume becomes relevent and IMFs happen
stronger IMFs mean _________ devations
more
more e- mean _________ devations
more
Density equation
D = m/v
grams / Liters
Density equation based on Ideal gas Law
P (MM) / RT
Molar Mass calculation based on Ideal Gas Law
DRT / P
Energy change for electromagnetic radiation equation?
E = hv
h = plank’s constant
v = frequency in s^-1
What is plank’s constant?
6.626 x 10^-34 Joule seconds
Speed of light equation
c = vλ
(speed of light) = (frequency in s^-1) (wavelength in meters)
Speed of light?
2.998 X 10^8 ms^-1
Beer’s law?
A = abc
(absorption) = (molar absorptivity) (path length) (concentration)
According to Beer’s Law, the higher concentration…
the higher absorption
1 torr= ?
1 torr = 1 mmHg
760 mmHg = 1 atm
Rf in paper Chromatography is…
(d of solute) / (d solvent)
non permanent dipole
london-disperson forces
what are ionic solids held together by
electrostatic attraction
Why are ionic solids unable to bend?
because they have a specific +/- attraction structure
Why are metallic solids able to bend?
because they have a random e- soup and they can bend wherever without disrupting the IMF
Why are covalent networks so hard to melt?
there are no free e-
according to Coulomb’s’ law, stronger charger and smaller distance means -
stronger attraction
amorphous structure
ranomdly arranged molecules in a solid
Crystalline structure
strictly arranged molecules in a solid
If temperature is held constant, a smaller molecule has a _______ speed than a larger molecule.
greater
Lower T means lower P
for real gases…
P is even lower due to IMF
Lower V means higher P
for real gases…
P is even higher due to mass being significant
Heterogenous
mixture of two or more unevenly mixed substances
Homogenous
mixture of two or more evenly mixed substances
In Chromatography what are the three components?
- mobile phase
- sample
- stationary phase
Beer’s Law
(Absorption) = abc
a = molar absorptivity
b = path length
c = concentration
microwave waves…
rotate the molecule
infared waves…
vibrate the molecule
visible waves…
makes the molecule glow - e- goes to higher state
Ultraviolet waves…
breaks the bonds because the e- is so excited
Transmittance
the amount that comes through the light
Transmittance equation
(Amount Out) / (Amount In)
Ion Dipole
the attractive force between a charged ion and a polar molecule
Average KE equation
3/2 x (R/N) x T
R = constant (8.314 J/mol . K)
N = Avogadro’s #
T = temp in K
absorption
the light that the substance absorbs
emission
the light that the substance emits - what we see
Different concentration means…
same emission, different absorption
larger molecules are __________ polarizable
more easily
