AP chem unit 3
Conversion from atm to mmHg
1 atm = 760 mmHg
Conversion from atm to torr
1 atm = 760 torr
Does the pressure under ideal conditions matter if molecules are different but the same amount of moles?
No because volume is irrelevant in ideal conditions and therefore the size of the molecules would not matter.
Formula for when there is low temperatures that mess with ideal conditions
P = nrT/VT - a(n/v)^2
Combined Gas Law
P1V1/T1=P2V2/T2
Boyle's Law
P1V1=P2V2 - pressure an volume are inversely related] - only works if temp is constant
Ideal Gas Law
PV=nRT - P = Pressure in atm - V = Volume - n = # of moles - R = 0.0821 L*atm/mol*K - T = temp in Kelvins
Maxwell-Boltzmann distribution
Shows the spread of energies that molecules of gas or liquid have at a particular temperature - as # of particles get bigger there is a wider range of KE (graph becomes higher and to the left) - higher temp then more variations in speed (graph becomes lower and to the right)
dipole-dipole forces
attractions between oppositely charged regions of polar molecules - only between two polar molecules - strength of interaction depends on strength of dipole moment (greater the dipole moment, greater the interaction)
intermolecular forces
attractive forces between molecules
wavelength and frequency formula
c = (v)λ c = 3.0 x 10^-34 m/sec (speed of light)
More ___________ molecules, the lower the boiling point
compact
Gas Density Formula
d=PM/RT - M = Molar mass
ways to separate mixtures
filtration, distillation, chromatography
Absorbance vs. Transmittance
low T = high A ------ DARK SAMPLE high T = low A ------ LIGHT SAMPLE
If energy of hydration is _____________ lattice energy then the compound will be soluble
greater than
Two types of mixtures
homogeneous and heterogeneous - homeogeneous mixture: uniform throughout - heterogenous mixture: composed of distinct phases/parts (each phase has different properties)
In all _______ and _________ atoms are held closely together
liquids, solids - liquids hold atoms almost as much as solids except there is a little more room to move past
amorphous
no orderly arrangement of atoms
lights are made of ____________
particles/protons
The larger the molecule, the more __________ the electron cloud is resulting in stronger ___________
polarizable; intermolecular forces
the path length and concentration are _________________ to the number of absorbing species.
proportional
Large mass of particles: small mass of particles:
small velocity big velocity
Use a _________ test tube when measuring absorbance
square (used when you need accurate width at test tube to calculate, finger prints will also effect readings so do not touch below a certain point on the test tube)
hydrogen bonding
strong attraction between hyydrogen atoms and the lone pairs of an adjacent electronegative molecule - hydrogen bonding can only occur with a H atom and F, O, or N.
vapor pressure
the pressure exerted by a vapor over a liquid
root mean square speed
u = sqrt(3RT/Mw) - Mw = molecular weight in Kg/mol - R = 8.31 Kg * m^2 / s^2*K*mol
when do gasses behave the most ideally
under high temperature and low pressure.
Interactions between nonpolar molecules
(Same thing as London Dispersion Forces) the electrons of a nonpolar molecule move from on side to the other and create a tempoary partial negative/positive charge on each side of the molecule. This charge then induces a dipole moment on another non-polar molecule which then interacts with the original one.
molecular solids properties
- Intermolecular forces holding it together - forces holding this together is weaker than ionic solids forces - lower melting point/boiling points (compound is ionic) - do not conduct electricity (all valence electrons are locked up into covalent bonds) - includes polymers.
Things that effect lattice energy
- charge magnitude - radius of ion (Coulombs law)
Inter molecular interactions involving a dipole
- dipole induced dipole - dipole-dipole - ion-dipole force
ionic solid properties
- low vapor pressure - high boiling point - high melting point - brittle
If intermolecular forces are strong
- low vapor pressure - high boiling points
covalent network solids
- mesh of covalent bonds holding atoms together (3D network of covalent bonds) - only forms between non-metals - has strong intermolecular forces - extremely high melting/boiling point
polar molecules can attract to
- other polar molecules - non-polar molecules - ions
Gas
- particles in constant random motion - no definite volume or shape
The greater the surface area of an isomer ______________
- the greater the attraction of intermolecular forces - the greater the boiling point is.
Two forces competing with each other every time an ionic compound is put into water
1) Energy of hydration(Solvent-solute attraction) - Energy associated with the attraction between the water molecules and the ions 2) Lattice energy - energy holding ions together in the crystal
radiation wavelength from shortest to longest
1) Gamma Ray 2) X-Rays 3) Ultra Violet 4) Visual Light 5) Infrared 6) Microwaves/radar 7) Radio
ranking intermolecular forces (strongest to weakest)
1) Ion-dipole 2) Hydrogen bonds 3) Dipole-Dipole 4) London Forces 5) Dispersion forces / Dipole induced dipole
Kinetic Molecular Theory
1) Molecules are so small we can ignore their volume (At STP, the volume of a gas occupied by a molecule is 0.01%) 2) The average Kinetic energy of a gas is proportional to temperature 3) Collisions between molecules are perfectly elastic(no energy lost)
Kinetic Molecular Theory (three parts acording to AP)
1) Particles have random, continuous motion 2) Collision are perfectly elastic (no stickiness) 3) Particles have negligible volume
radiation frequency from shortest to highest
1) Radio 2) X-rays 3) Ultra Violate 4) Visual Light 5) Infrared 6) Microwaves/radar 7) Radio
A student is asked to prepare a 2.5 M solution of AgNO3. The student must prepare 100 mL, describe the steps the student will use.
1) convert to moles (using the Molarity as a conversion factor.) 2)convert to grams (using molar mass) 3) Measure out the calculated grams in the previous step 4) Add small amounts of water to the flask 5) place the sample into the volumetric flask and then fill the flask with water until the volume is 100mL
relationship between: 1) boiling point and vapor pressure 2) melting point and vapor pressure 3) melting points and boiling point
1) inversely related (as boiling point rises, vapor pressure decreases) 2) inversely related (as melting point rises, vapor pressure decreases) 3) directly related (rise with each other)
Beer-Lambert Law
A = ebc - Amount of light absorbed is directly related to concentration of a solution. A = absorbance e = extinction coef. b = path length (width of test tube) c = concentration
Mixtures
A combination of two or more substances that are not chemically combined
pressure and temperature relationship not in ideal conditions
At lower temperatures, real gases have lower pressures than the ideal gas law will calculated. - Low temperature means low kinetic energy, which means intermolecular forces attract molecules and fewer strike each other/sides of the container.
Isomers
Compounds with the same formula but different structures.
Energy of a photon
E = hf or E = hc/λ h = plank's constant (6.63 x 10^-34 J*S)
Kinetic Energy of a gas equation
KE = 1/2 mv^2
If two molecules are of significantly different sizes and experience different IMFs, how should you compare?
In some cases, size effects can be larger than effects from IMF differences. A good way to determine is to use experimental data such as boiling point.
If two molecules have approximately the same number of electrons (which typically also means the same mass) how do you compare?
Look at intermolecular forces hydrogen > dipole-dipole > LDF
What properties of substances can be explained by intermolecular forces?
Melting point/boiling point Direct relationship (increase as IMFs increase) Vapor pressure Pressure exerted by a gas when it is at equilibrium with its liquid (in a closed container) Inverse relationship (decrease as IMFs increase) Volatility Ease of evaporation Inverse relationship (decrease as IMFs increase) Surface tension Ability of the surface of a liquid to resist an external force Direct relationship (increase as IMFs increase) Viscosity Resistance to flow Direct relationship (increase as IMFs increase) Heat of vaporization Energy required to convert a liquid to a gas Direct relationship (increase as IMFs increase)
pressure and volume relationship not in ideal conditions
Pressure and volume relationship deviate from ideal gas law when there is high pressure - b/c the amount of space the molecules have to move is really small, they start to take up significant amount of volume. - under high pressure predicted amount will be lower than actual for both volume and pressure.
Dalton's Law of Partial Pressures
Pt = Pa + Pb + Pc states that the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture
non-ionizing radiation
Radiation that has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to remove electrons
STP conditions
Standard Temperature and Pressure: 273.13 K (0ºC) at 1 atm
Absorbance
The amount of light absorbed by a sample - 2 - log%T = A - ranges from 0 to infinity
Transmittance
The amount of light that passes through the sample. - Pe/Pf x 100 = T - ranges from 0% to 100%
photoelectric effect
The emission of electrons from a material when light of certain frequencies shines on the surface of the material - Light must have a specific frequency or higher - Intensity of light effect rate the electrons are ejected but not if they will be.
London dispersion forces
The intermolecular attractions resulting from the constant motion of electrons and the creation of instantaneous dipoles - found in all molecules - in large molecules, london forces are strong - more electrons = stronger force / higher molecular weight = stronger force
If two molecules have significant differences in number of electrons and the same types of IMF, how should you compare?
The larger the molecules, the stronger IMFs
dipole-induced dipole
The partial charge on a polar molecule induces a temporary partial charge on a neighboring non polar molecule or atom. The charge on the polar molecule has to be very strong.
atmosphere (atm)
a unit of pressure based on the average pressure of air at sea level
How to decided what wavelength to use when measuring absorbance?
Use wavelength that is best absorbed by the concentration (having one wavelength reduces reaction between molecules and light in the compound) - To do this test different wavelengths
Ideal gas law equation when there is high pressure
V = (nRT / P) + nb - n = # of moles - b = vanderwaals constant (L/mol) and unique for each gas.
Charles' Law
V1/T1=V2/T2 - temperature and volume are directly related - have to use Kelvins (C + 273)
Avogadro's Law
V1/n1=V2/n2 - number of moles and volume are directly related
mole fraction equation
Xi = ni/ntotal - proportional to partial pressure - ni/ntotal = Pi/Ptotal - Pi = Xi x Ptotal
Distillation
a liquid is boiled to produce a vapor that is then condensed into a liquid
molar absorptivity
a measure of how strongly the sample absorbs light at a particular wavelength.
Chromotography
a process which separates the parts of a solution with special paper and a solvent. - The further up the die of a molecule is the more attractive it is to the solvent whereas the lower die is attracted more to the stationary phase of the paper. - If you have a polar mobile phase/solvent then the farther up the paper, the more polar it is (this flips when a non-polar solvent is used)
crystalline
an orderly, repeating arrangement of atoms or molecules in a solid
Ultra violet/ visible radiation is associated with transitions in _________ ____________ levels
electronic energy
ionizing radiation
enough energy to dislodge electrons from atoms, forming ions; capable of causing cancer (gamma, X-rays, UV)
Microwave radiation is associated with transitions in ____________ ____________ levels (AP video not in class)
molecular rotational
Infrared radiation is associated with transitions in ___________ ____________ levels
molecular vibrational - vibrational states of bonds require more energy than molecular rotations
Molarity
moles of solute/liters of solution
Vibrational states of bonds
require more energy than molecular rotations; Infrared radiation has a higher energy per photon than microwave(higher frequency and shorter wavelength)
electromagnetic spectrum
the complete range of electromagnetic waves placed in order of increasing frequency
thresehold frequency
the minimum frequency needed for a light to eject electrons out of a metal.
Filtration
the process that separates a solid from the liquid in a heterogeneous mixture
ion-dipole forces
the result of electrical interactions between an ion and the partial charges on a polar molecule. - affected by charge of ion and strength of dipole moment.
Spectroscopy
the study of matter's interactions with electromagnetic radiation.
The stronger the intermolecular forces the more ______________ a substance is.
viscous
