chem 120
What's an isotope?
Atoms that have the same number of protons but a different number of neutrons
What's an allotrope?
different molecular forms of the same element
S2, S8, and S20 are all examples of what?
allotropes of S
what is atomic number?
equal to the number of protons in the nucleus of any of its atoms
how does a mass spectrometer work?
It operates on the principle that an atom or molecule, once ionized, can be deflected by a magnetic field. The amount that it's deflected depends on the speed of the particle, the strength of the magnetic field, and the mass-to-charge ratio
what's a mass spectrum
a graph of intensity versus the mass-to-charge ratio
relative abundances
one isotope more abundant than the other
average atomic mass
weighted average of the masses
atomic mass interval
used for certain elements to indicate the range of values expected for the atomic mass because of observed variations in the isotopic abundances of these elements. [a,b] form, >=a <=b
conventional atomic mass
the mass you use when you need a representative value when given a range of masses
synthesis
a+b->ab, two or more come together
decomposition
ab->a+b, one reactant breaks down into two or more simple reagents
single displacement
ab+c->cb+a, one element is replaced by another more reactive element (eg. redox)
double displacement
ab+cd -> ad+cb, pos or neg ions of two ionic compounds replace each other (eg. ppte)
combustion
A compound reacts with an oxidant (usually oxygen) in a highly exothermic reaction. For hydrocarbons, the products are carbon dioxide and water.
Acid-Base
A proton is transferred from a proton donor (acid) to a proton acceptor (base).
proton donor
acid
proton acceptor
base
solution
homogeneous mixture of one or more solutes in a solvent
homogeneous
uniform composition, right down to the molecular level; the molecules of one substance are mixed uniformly amongst the molecules of the others
solvent
determines the phase of the solution (i.e., solid, liquid, or gas); usually the most abundant component
solutes
all other components of the solution
aqueous solns
Aqueous solutions have water as solvent
comprised of positive and negative ions
ionic compounds
arranged in regular, repeating patterns
ionic compounds
the ions are held in their positions by strong bonding forces
ionic compounds
typically solids at room temperature
ionic compounds
when this type of solid dissolves in water, positive and negative ions break away from the solid surface and become “hydrated”
ionic compounds
dissociate not dissolve (creates ions in a soln)
ionic compounds
comprised of stable, neutral molecules
molecular compounds
the compound may be solid, liquid or gas at room temperature depending on the strength of the intermolecular attractions
molecular compounds
typically dissolves not dissociates, molecules become hydrated in water
molecular compounds
precipitate
insoluble solid formed from the solution
proton transferred from _____ to ________ in lowrey bronsted acid base rxns
acid to base
hydrochloric acid
strong
HBr hydrobromic acid
strong
HI hydroiodic acid
strong
HClO4 perchloric acid
strong
HBrO4 perbromic acid
strong
HIO4 periodic acid
strong
H2SO4 sulfuric acid
strong, diprotic
HNO3 nitric acid
strong
group 1 hydroxides: LiOH, NaOH, KOH, RbOH
strong bases
group 2 hydroxides: Mg(OH)2, Ca(OH)2, Sr(OH)2, Ba(OH)2
strong bases
When do neutralization reactions essentially go to
completion
If either the acid or the base is “strong”
What do acid-base neutralization rxns typically produce?
salt & water (water often but not always)
theo yield
max amount of product that can be produced
limiting reagent/reactant
the species that limits the amounts of product that can form (runs out first)
consecutive rxns
a series of reactions that occur sequentially; the products from one reaction are consumed as reactants in a subsequent reaction (can add)
t or f: can add together consec rxns
true
t or f: can add together simultaineous rxns
false
simultaneous rxns
reactions that are independent and occur at the same time
another name for simultaneous rxn
independant
green chemistry
an approach to chemistry that is intentionally focused on not only the efficient use of atoms (and energy) but also chemical methods that reduce or eliminate reagents, products, solvents, by-products, wastes, etc. that are hazardous to human health or the environment.
atom economy
defined in terms of the theoretical amounts of reactants and products involved in a reaction or process (is a percentage)
% atom economy eqn
(stoic mass of desired prod (only) / mass of a stoichiometric mixture of reactants) x 100%
stoichiometric mass
the maximum mass that can be expected from a stoichiometric mixture of reactants
stoichiometric mixture
the mole ratio of reactants is equal to the ratio of the stoichiometric coefficients. None of the reactants is present in excess.
higher atom economy is better or worse?
better, we want higher percent atom economy
e-factor/environmental factor
quantity that can be calculated by a chemist to help assess the “green-ness” of a chemical reaction or process, defined in terms of quantities that are easily measured
e-factor eqn
mass of waste produced / mass of product obtained
does water count as a waste product when calculating e-factor?
no
bigger or smaller e-factor is better?
small. A large value for the E-factor indicates that many kilograms of waste are generated for every kilogram of product obtained. A small value for the E-factor is desirable
what is this called: When an electron is “confined” to a finite region of space by the forces exerted on it, its total energy is restricted to certain special values!
quantization
what does light being em radiation that transmits energy through space or some other medium mean?
Light has an electric field that oscillates at a certain frequency, and a magnetic field that oscillates at the same frequency, perpendicular to the plane of the electric field
how is em radiation produced?
when electrical charges (e.g. electrons) undergo some sort of
acceleration
Wavelength
distance between successive maxima (m)
period (T)
time it takes for the electric field to return to its maximum strength (s)
frequency
# of times per second the electric field reaches its maximum value, (s^-1), inverse of period
t or f: gamma rays have more energy than x-rays
t
t or f: gamma rays have more energy than radio waves
t
t or f: gamma rays have a higher frequency than radio waves
t
t or f: gamma rays have a larger wavelength than radio waves
f
starting from largest wavelength and going towards smallest wavelength (highest freq), what comes after radio waves?
microwaves
starting from largest wavelength and going towards smallest wavelength (highest freq), what comes after microwaves?
infrared
starting from largest wavelength and going towards smallest wavelength (highest freq), what comes after infrared?
vis light (roy g biv)
starting from largest wavelength and going towards smallest wavelength (highest freq), what comes after visible light?
ultraviolet
starting from largest wavelength and going towards smallest wavelength (highest freq), what comes after ultraviolet?
x rays
starting from largest wavelength and going towards smallest wavelength (highest freq), what comes after x rays?
gamma rays
visible light region
about 400nm-750nm
What is blackbody radiation?
Regardless of composition, an object at 300 K will emit light in the mid-IR region. (Atoms in a heated solid oscillate with certain energies only)
The Photoelectric Effect
photoelectric effect, light is used to dislodge electrons from the surface of a metal
three things learned from photoelectric effect
1. electrons were ejected only if the frequency of light was greater than some “threshold” frequency
2. kinetic energy of e- increased proportionally w frequency for frequencies greater than threshold frequency
3. electrons were ejected instantaneously (no observable time delay) regardless of the intensity of the incoming light
work function
the minimum energy required to dislodge an electron from the metal’s surface
Line spectra of atoms
The emission spectrum of any substance can be obtained by energizing the sample of material. prisims split white light so place atomic gas sample btwn. will create dark lines showing quanta of energy were absorbed by the atomic gas. Alternatively, if the light emitted from a sample of high energy atoms is dispersed into its component wavelengths, only certain colours of lines appear. (absorption or emission spectrum created showing the quantization of energy)
what experiment showed the energy of light is highly localized and proportional to it's frequency?
photoelectric effect
who did the photoelectric effect
einstein
who did blackbody radiation
planck
key takeaway from line spectra & atoms
The energy of an electron in an atom is not arbitrary, but rather, it is restricted to have certain “special” values
radius of 1s orbital, Bohr radius
52.9 pm
why are all energies negative for energy level diagram of H atom
E = 0 when e- is infinitely far away (from nucleus). If dist decr, eng does too... therefore it's neg for all dist other than infinitely far away
as n -> infinity (aka 7...)
dist btwn energy levels -> 0 (less space between eng lvls as n gets larger)
When the electron “drops” from a higher energy level (Eupper) to a lower energy level (Elower), the atom emits a photon with energy equal to ________
Eupper − Elower
In order for the electron to “jump” from a lower energy level to a higher energy level, the atom must absorb a photon with energy equal to _________
Eupper − Elower
what were the 3 problems w bohrs model for the H atom
1. cannot extend it to other atoms
2. doesn't explain why H doesn't emit radiation conti
3. doesn't actually explain WHY the ang mom is quantized, just knows that is HAS TO BE (conditions were imposed)
what was de brog's hypoth that helped describe behaviour of e- in atoms?
wave-aprticle duality
what was heisenberg's principle that helped describe behaviour of e- in atoms?
Heisenberg uncertainty principle (can never know true behaviour of a system)
Diffraction suggests light behaves as a _____
wave
The photoelectric effect suggests light behaves as _______
particles
diffraction
when light passes through a hole or slit whose size is comparable to the wavelength of the light (con & des int. of waves make diffraction patterns)
Heisenberg Uncertainty Principle
impossible to know simultaneously both the position and the momentum of a particle with absolute certainty
meaning of psi squared (schro wave eqn)
prob of finding the e- at a particular point
quantum numbers: n
principal quantum number (size, aka what period it's in), first quantum #, goes from 1-7 & is really just what shell it's in
quantum numbers: l
orbital angular momentum quantum number (determines the “shape” of an orbital), second quantum #, (basically, is just waht type of orbital it's in. so s = 0, p = 1, d = 2, f = 3)
quantum numbers
4 digits that represent where the e- is (like a lil coord sys)
quantum number: ml
magnetic quantum number (third quantum number), the number of ml values tells us about the number of distinct orientations that are allowed for a particular orbital, basically, is just WHERE it is WITHIN the shell. bc s only has one slot, it has to be 0. p has 3 diff slots/types of orbitals so it goes -1, 0, 1 (L->R), d goes -2, -1, 0, 1, 2, middle is always 0, right is pos, left is neg, etc, you get it...)
quantum number:
ms, spin number, is just + or - 1/2 (doesn't really matter) it's just for the orientation. cannot have two in the orbital the same spin direction (must always be opposite each other but doesn't matter which is which)
t or f: for energy lvl diagrams for all atoms the s, p, and d orbitals are equal the diff n levels (eg. 3s has energy as 3p and as 3d)
no. only H
Probability density plots
like a scatter plot
how do nodes appear in Probability density plots
as surfaces -- planes or cones
# of radial nodes =
n - l - 1
# of angular nodes
l
# of total nodes
n-1
p orbital shape
dumbbell
s orbital shape
sphere
Boundary Surface Plots
balloon plots
balloon pictures
shape and directionality of the orbital. In most cases, such a plot does not convey information about how the probability (or density) varies within that region of space. as n inc, size inc
what do the diff colours mean for balloon plots
The colours (shades) on the lobes of the orbitals are used to indicate the phase (i.e. sign)
if it's 2px balloon plot, what axis does it lie on?
x-axis. can extend this to y and z too...
which d orbital has a ring and two little balls at the top and bottom?
3dz^2
t or f: for balloon plots, if given 3xy that means the orbitals lie in the xy plane
true
t or f: the + and - signs on the balloon plots represent the charge
umm no obvs not... it's an e-... net charge always gonna be neg... the + and - are for the phase (the sign of the wave)
Radial factors
R(r) vs r
t or f: R(r) decreases exponentially as r increases
true
R(r) crosses the r axis n−l−1 times. how many radial nodes does it have?
n-l-1 (aka the number of times that it crosses the x-axis)
t or f: for p shells, (l = 1) the R(r) vs r graph has it's max value at r = 0
falseeeee. for S SHELLS NOT P!!! l = 0 (not 1!!!)
t or f: for all states other than s, R(r) vs r has a value of 0 at r = 0
t (BUT FOR S, IT'S THE MAX POINT AND AS r -> 0, R(r) -> infinity
Radial Electron Densities
R(r)^2 vs r, like walking from the centre out
What are the 2 interpretations of R(r)^2 vs r plots?
1. how the probability of finding the electron changes as we move away from the nucleus in a certain direction.
2. how the density of the electron “cloud” changes as we move away from the nucleus in a certain direction
General features of radial electron density plots R(r)^2 vs r (3)
1. series of maxima that get progressively smaller as r increases
2. for “s” states, the density is greatest at the nucleus
3. for “p” , “d”, “f”, etc. states, the density is zero at the nucleus
Radial Distribution Plots
r^2R(r)^2 vs r, aka Radial Distribution Function (RDF)
the value for r at the max value the RDF attains is what?
most probable distance between e- and nucleus
general features of RDF (aka r^2R(r)^2)
1. series of maxima, get progressively bigger
2. all plots start out at zero
3. number of maxima = n-l
The electron moves around the nucleus in a(n) ________ which has a particular size, shape, and orientation
orbital
The lowest energy atomic orbital is the ___ orbital. It is a ________ orbital. When the electron occupies this orbital, the most probable distance between the electron and the proton (nucleus) is ao = ________
1s, spherical, 52.9pm
t or f: the state of an e- is described by a set of quantum numbers. this set of numbers does not need to be unique
f. it does need to be unique...
The energy of a state is given by En = ______
Rh/(n^2)
t or f: for a multielectron atom, the orbitals in the same “shell” are of the same energy (s < p < d < f, etc.)
false bc of e- e- repulsion, s lowest then p then d...
How do electrons distribute themselves to obtain the lowest possible energy for the atom? (3)
1. Aufbau Procedure
2. The Pauli Exclusion Principle
3. Hund's rule
What does the Pauli exclusion prinicple state?
No two electrons can have the same set of quantum numbers n, l, ml, and ms.
What is the Aufbau Procedure?
that weird triangle thing that u can acc just use the periodic table for (basically just the order orbitals are filled in for neutral atoms)
What are the two exceptions to the Aufbau (atoms w atomic num <=36)
Cr and Cu
What is the electron configuration for Cu and why
1s2, 2s2p6, 3s2p6d10, 4s1
Fills 3d before 4s. For some reason a completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital.
What is the e- config for Cr and why?
1s2, 2s2p6, 3s2p6, 4s1, d5
Cr is an exception where the last electron enters into the 3d orbital instead of 4s orbital to attain half-filled stability
What does Hund's Rule state?
If there are not enough electrons to fill completely a set of energetically degenerate orbitals, the lowest energy arrangement is the one which has the maximum number of parallel spins. When electrons have parallel spins, they avoid each other to a greater extent. (fill each thing in the p or d once before going back for seconds)
energetically degenerate
are of equal energy
When electrons have parallel spins, they avoid each other to a greater extent. Thus, they shield each other less and this increases the attraction each electron feels towards the nucleus. The increased electron-nucleus attraction results in a ______ total energy for the atom
lower
The rows of the periodic table are called ______.
periods
extra for funsies: each period starts a new shell, there are 7 periods
The columns are called _______
groups
alsooo:
they're labelled 1-18 and provide info abt # of valence e- in the atom
valence electrons
e- in the outermost shell of an atom. They are the electrons that participate in bond formation
t or f: exceptions to aufbau exist other than Cu and Cr
true, there are actually lots for atoms w/ atomic numbers of 36 and above (but we aren't expected to know what they are so don't stress)
diamagnetic atoms
all electrons are paired; the atom does not possess a magnetic moment; the atom interacts only weakly with an external magnetic field
paramagnetic atoms
one or more unpaired electrons; the atom possesses a magnetic moment; the atom interacts strongly with an external magnetic field
what does it mean if something "possesses a magnetic moemnt"?
there are unpaired e- and the mag fields do not cancel
atomic radii _______ across a period (L to R)
decrease
atomic radii __________ down a group (T to B)
increase
covalent radius
½ of the diatomic bond length for the X2 molecule½ of the diatomic bond length for the X2 molecule of X
metallic radius
½ of the distance between “nearest neighbours” in a metallic solid
Atomic Radii
size
Ionization Energy
energy required to remove an electron from a gas-phase atom (often reported as an enthalpy change, ΔH)
Why is IE(1) < IE(2) < IE(3)...
It becomes increasingly difficult to remove electrons if one or more electrons have already been removed
Ionization energies ________ down a group
decrease
Ionization energies generally ________ across a period (but there are easily explained exceptions!)
increase
t or f: IE and atomic radii follow the same trends
false. they're opposite bc it's easier to remove an e- from something larger bc it has a lesser hold on it's e-
Why does IE decrease as we move from Be to B?
The 2p electron in B is in a higher energy orbital and
is easier to remove than the 2s electron in Be
Where are the two "dips" in IE?
groups 2 -> 13 (intuitive)
groups 15 -> 16 (think N -> O, no definitive reason why)
Electron Affinity (EA)
energy change that accompanies the addition of an electron to a gas-phase atom
t or f: EA mostly trends towards the top right corner
true
which groups do not release energy when they acquire an e-?
2 and 18 (full orbitals)
which two elements have the largest EAs?
O, F
where does polarizability trend towards?
bottom left corner
transfer of e-
ionic
sharing of e-
covalent/molecular
octet rule
An atom exhibits the tendency to attain a noble gas configuration either by sharing or transferring electrons.
t or f: lewis structures are almost never used for molecular compounds
nah that's f. almost exclusively for covalent bonding (bc think about ionic really quickly, one's just gonna be full and the other is gonna be empty... doesn't really show that much)
t or f: the H atom never forms more than one bond and is always a “terminal” atom
t, can only have 2 e- in the valance shell (ever)
t or f: 2nd row atoms never have more than 8 valence e−’s
true
t or f: C, N, O and F atoms almost never have less than 8 valence e−s around them
t
Atoms from the _______ period (and beyond) might have an “expanded” octet (more than 8 valence e−’s)
3rd
formal charge formula
(the number of valence electrons that atom X brings to the molecule) - (the number of valence electrons “owned” by atom X in the structure under consideration)
# e−’s owned =
# lines + # dots
lines =
½ × # bonding electrons
the sum of the formal charges must always equal ____________
the total charge on the molecule or ion!!
t or f: The “true” structure is a hybrid (weighted average) of the resonance structures
t
t or f: try to place like formal charges (eg +1 and +1) on adjacent atoms
f, Avoid placing like formal charges (e.g., +1 and +1 or −1 and −1) on adjacent atoms.
Resonance structures
have the same spatial arrangement of atoms, but a different distribution of electrons around the atoms
t or f: you should try to place formal charges according to electronegativity, if possible (on the more electronegative atom)
t, (e.g. in the NCO− ion, it is better to place the −1 formal charge on O rather than N because the O atom is more electronegative than the N atom).
t or f: almost always, formal charges do not exceed ±1.
t
have the same spatial arrangement of atoms but a different distribution of electrons around the atoms
resonance structures
t or f: All resonance structures are considered equivalent
f, may be considered equiv or non-equiv need to look at formal charges (if lewis structures show same energy then you're good and if not then eeeee not equiv)
t or f: when drawing resonance structures it's okay to break a sigma bond
f, skeletal structure must remain unchanged
t or f: when drawing resonance structures it's okay to break a pi bond
t, sure that's kinda the point
Delocalized electrons
e- not associated with a single atom but can be distributed between 3 or more atoms
Resonance structures only exist if there is a ________ bond in the structure
double (or triple), (but not all structures with double or triple bond can have resonance structures)
t or f: Electrons forming single (sigma) bonds are may be delocalized
f, never.
t or f: Electrons in lone pairs, or double- or triple-bonds (pi bonds) may be delocalized
t
Lattice Energy
energy released when gas phase ions combine to form an ionic solid
The greater the charges on the ions, the _______ the lattice energy
greater
The smaller the ionic radii, the _______ the lattice energy
greater
the strength of a covalent bond depends upon what 3 things
1. sizes of atoms
2. bond-order
3. polar or non-polar
Bond length _______ and bond strength ________ as the bond order increases
decreases, increases
electronegativity
provides a quantitative measure of the “pull” an atom has on the electrons in its bonds
what are the most electronegative elements?
F, O, Cl and N
When electron pairs are not shared equally, the bond will have ___________ because one end of the bond will be slightly positive (+δ) and the other will be slightly negative (-δ)
a dipole moment
are polar covalent bonds or pure covalent bonds generally stronger?
polar covalent bonds, because they're partially covalent and ionic (and ionic are stronger)
VSEPR Theory
Valence Shell Electron Pair Repulsion Theory, groups arrange themselves around an atom to minimize electron pair repulsions.
are carbon atoms are explicitly shown line-angle structures
no but are at ends and points
t or f: for line angle structures, hydrogen atoms are explicitly shown when bonded to carbon atoms
f
for line angle structures, lone pairs may or may not be explicitly shown. Need to be able to identify the number of lone pairs by the presence or absence of _______
formal charges
valence bond theory (VB theory)
a “localized orbital approach”
We think in terms of orbitals that belong to individual atoms in the molecule
vb theory
We imagine building a molecule atom-by-atom using appropriate atomic orbitals
vb theory
An atomic orbital helps us visualize how a single electron interacts with one nucleus
vb theory
useful for describing the groundstate properties of molecule (e.g. geometry)
vb theory
used extensively in organic chemistry
vb theory
molecular orbital theory (MO theory)
a “delocalized orbital approach”
We think in terms of orbitals that belong to the molecule
mo theory
We imagine building a molecule electron-byelectron using appropriate molecular orbitals
mo theory
A molecular orbital helps us visualize how a single electron interacts with two or more nuclei
mo theory
useful for describing excited-state properties, spectroscopy, and chemical reactions
mo theory
used extensively in inorganic and physical chemistry, and increasingly in organic chemistry
mo theory
orbital overlap (vb theory)
used to describe formation of a covalent bond when unpaired electrons on two different atoms “pair up” and are shared by both atoms
sigma bond (vb)
overlap along internuclear axis, single bond
pi bond (vb)
overlap off axis (like reaching), sideways overlap of orbitals, double & triple bonds only
t or f: pi bonds can be used for a single bond (vb)
f, only double and triple, sigma for single
which type of bond in vb theory overlaps along the nuclear axis?
sigma
Orbital Hybridization
Take “n” atomic orbitals and mix them to generate “n” hybrid orbitals
s + pz
two sp orbitals 180o apart
s + py + pz
three sp2 orbitals pointing towards the corners of an equilateral triangle
s + px + py + pz
four sp3 orbitals pointing towards the corners of a tetrahedron
2 groups (vb)
linear, sp
trigonal planar (vb)
3 groups, sp2
tetrahedral
four groups, sp3
which is the highest energy? sp, sp2, sp3
sp (50/50 split), sp2(33/67), sp3((25, 75). s is higher energy than p
often involves overlap of hybrid orbitals (vb)
sigma bonds
can be formed via the overlap of unhybridized p orbitals (vb)
pi bonds
double bond = (vb)
1 pi + 1 sigma
triple bond = (vb)
1 sigma + 2 pi
trigonal bipyramidal
sp3d, 5 groups
tells us how a single e- interacts with all of the nuclei
molecular orbital theory (mo)
MO Theory: Key concepts (3)
1. The valence electrons in a molecule occupy orbitals that extend, in principle, over all nuclei in the molecule
2. We imagine that the valence orbitals of the atoms are transformed into a set of molecular orbitals as the atoms combine to form the molecule (n atomic orbitals -> n molecular orbitals)
3. Some MOs promote bonding and others don’t. Sometimes, an MO makes no contribution to bonding. Consequently, MOs can be classified as bonding, antibonding or nonbonding.
The appropriate MOs are obtained by combining the AOs in
two ways: _________ and ___________
constructively, destructively
A bonding MO is ______ in energy than the AOs from which it is derived. The antibonding MO is ________ in energy than the AOs from which it is derived
lower, higher
One combination of AOs produces a __________ and the other produces an __________
bonding orbital, antibonding orbital
t or f: antibonding MOs have a nodal plane perpendicular to the bond axis
t
t or f: t or f: bonding MOs have a nodal plane perpendicular to the bond axis
f
sigma orbitals (mo)
arise from s or p orbitals that overlap along the internuclear axis
pi orbitals (mo)
arise from p orbitals that overlap “off-axis”
t or f: for mo, you fill the energy lvl diagrams using The Pauli Exclusion Principle and Hund’s Rule apply
t
bond order =
(bonding e- - antibonding e-) / 2
t or f: for a homonuclear diatomic molecule to be stable, the bond order must be zero
f, must be greater than 0
in general, _____ bonds are slightly higher energy than pi bonds in mo. this isn't the case for ___ and ____.
sigma, F2 and O2 (2p bonding sigma is lower than the 2p bonding pi, like a diamond)
The main assumptions of kinetic molecular theory are: (6)
1. gas molecules v small & far apart (mostly empty space)
2. molecules in constant random motion
3. molecules collide with each other and walls of container (pressure)
4. collisons are completely elastic (kin eng conserved)
5. no attractive or repulsive forces between molecules
6. average translational kin eng is proportional to temp
when are there deviations for PV = nRT?
Deviations from ideal behaviour are most significant when the PRESSURE is VERY HIGH or the TEMP is VERY LOW
the sum of the partial pressures is equal to _______________
the total pressure
If we assume ideal gas behaviour, then for fixed values of T and V, the partial pressure of A depends on ________
the number of moles of A and the total pressure depends on the total number of moles of gas
The ideal gas model is obviously not perfect. It neglects (2)
1. size of molecules themselves
2. intermolec forces
what does a mean in Van der Waals gas eqn
provides a measure of the strength of the intermolecular forces
what does b mean in Van der Waals gas eqn
provides a measure of the sizes of the molecules
solid -> gas
sublimation
gas -> solid
deposition
gas -> liquid
condensation
liquid -> gas
vaporization/evaporation
liquid -> solid
freezing
solid -> liquid
fusion
In solids, the molecules are often, but not always, arranged in __________
regular, repeating patterns
vapour pressure
pressure of vapour that forms above a liquid in a closed container
normal boiling point
temperature at which the vapour pressure of the liquid equals 1 atm
surface tension
energy required to increase the surface area of a liquid
viscosity
provides a measure of a fluid’s resistance to flow; the speed of flow through a tube is inversely proportional to the viscosity
t or f: the viscosity is higher when imf are stronger
t
relation btwn intermolec attractions, boiling point, surface tension, viscosity, and vapour pressure
In general, the stronger the intermolecular attractions, the higher the boiling point, the greater the surface tension, the higher the viscosity, and the lower the vapour pressure
a dipole moment
arises when bond dipoles in a molecule do not totally cancel. A non-zero dipole moment indicates that there is a separation between the centres of positive and negative charge in a molecule
polarizability
provides a measure of the extent to which its charge cloud can be distorted (polarized) by another molecule
the larger the molecule, the larger the ________
polarizability
London dispersion forces (LDFs)
most attractive when the molecules are large, always contribute to the molecular interactions
Hydrogen bonding forces
hydrogen atom bonded to N, O or F, the H atom carries
a significant positive charge and it is strongly attracted to a lone pair on another molecule, typically stronger than dipole-dipole or London dispersion forces, but they are still weak in comparison to covalent and ionic bonding forces
intermolecular hydrogen bond
“bridges” two molecules
intramolecular hydrogen bond
bridges two parts of the same molecule
The stronger the intermolecular attractions, the greater the:
- boiling point
- viscosity
- surface tension
- enthalpy of vaporization
The stronger the intermolecular attractions, the lower the:
- vapour pressure