moad Flashcards
1
Q
closed system
A
heat can exchange, not material
2
Q
isolated system
A
heat nor material can be exchange with its surroundings
3
Q
energy
A
work capacity
4
Q
work
A
change in molecular motion in a uniform way.
5
Q
heat
A
change in molecular motion in a chaotic way
6
Q
adiabatic
A
heat cannot be exchange with the environment, temperature changes
7
Q
isothermal
A
heat can be exchange with the environment, and temperature remains constant, in a water bath
8
Q
heat is
A
irreversible
9
Q
work is
A
reversible
10
Q
heat and work are
A
path functions
11
Q
state functions state that
A
path is not important
12
Q
internal energy
A
state function were KE + PE
13
Q
0TH LAW
A
if a is in thermal equilbrium with b and b is in thermal equilibrium with c, a and c are in thermal equilibrium
14
Q
1st law
A
for an isolated system, energy is constant
15
Q
Show the 1st law as a formula
A
delta U = q + w
16
Q
What does applying heat does to the population levels
A
-same seperation
- different population
17
Q
cp mean
A
constant pressure
18
Q
constant pressure for chemist is…
A
important
19
Q
what is the definition of heat capacity
A
heat capacity is the ability to raise the temperature by 1k
20
Q
in episode 4 , if the beta is equal to temperature what does this mean?
A
this means that the levels are partially filled.
21
Q
enthalpy
A
heat change at constant pressure
22
Q
isobaric
A
same
23
Q
solids and liquids take up
A
little volume , therefore little volume change occcurs at these states
24
Q
what happens in irreversible expansions
A
the surroundings do not have time to adjust to the equilbrate with the systems, therefore it does not provide the maximum energy for work
25
what happens during expansions?
the seperation between energy levels decreases. in uniform reversible expansion it is repopulated in scale according to boltzmann
26
what happens to the energy levels in adiabatic reversible expansion
energy levels seperation decrease, but population is constant/ equilibrate
this shows temperature decrease
27
Hess law
the standard enthalpy change of a reaction is the sum of all the standard enthalpy individual reactions that the main reaction can be separated into
28
heat capacity changes for
each temperature
29
more work is done for cp than cv why so
force pushing to increase volume
bond stretches
30
Spontaneous reactions are
irreversible and do not need any interventions
31
what happens to entropy of the universe during a spontaneous reaction
it increases, to reverse the reaction requires a lost of entropy of the universe which is against the 1st law
32
2nd law
energy spontaneously tends to moves from a highly concentrated region and diffuses and spreads out
33
how is chaos prevented
activation energies
being delayed/ so slow
34
what is theorised
the end of the universe will end when there is complete disorder
35
entropy
energy quality that leads to spontaneous changes
36
entropy is
additive and a state function
37
entropy has a
inverse relationship between temperature. at high temperatures additional heat to system has a smaller influence to entropy
38
why is water greater than troutons law=?
water liquid has hydrogen bonding, this means it has more order compare to other liquids, therefore a greater enetropy change occurs when changing from liquid to gas.
39
why is acetic acid have a lower value than troutons law?
this is because there is more order than expected in gaseous forms
40
entropy is a law of probability, therefore ....
it does not apply to large traditional size things eg the water bottle is not constantly moving
41
3rd law
entropy of perfect crystal is = 0
42
slow cooling
s =0
43
why is entropy nor 0 during fast cooling
molecules cool too quickly before they can rearrange themselves to the lowest energy configuration
44
h can tell if
reaction is exo or endothermic
endo = + exo = -
45
hemoltz value is useful for
scientist that use cnstant pressure, A.
46
for solids and liquids pressure and volume are
independant
47
for solids and liquids gibbs and pressure are almost
independant
48
chemical potential
ability to take part in chemical processes ei reactivity potential energy
49
if a gas / liquid is in equilbrium, this means that
g = 0
chemnical potential are same
no driving force to chzange
50
why is water gas at 120
lowest chemical potential at that temp.
most stable
51
gases have
the greatest molar entropy
52
how do ice skates work
temperature is constant but there is a pressure change, this causes the ice to melt to liquid phase - it crosses the solid liquid boundary
53
why does ice melt when you are standing?
Because ice is less dense than liquid water, its melting point is lowered under high pressures. A long-standing theory says that this is what causes ice to be slippery: As you step on it, the pressure of your weight causes the top layer to melt into water
54
how do pressure cookers work
increases the boiling point of water
food can cook at higher temperatures
55
gibbs free energy relies on
amount of substance/ moles
56
ideal gas
no chemical reactions
57
why is enthalpy 0 is ideal mixing
no bonds or reaction takes place purely entropic.
58
for mixing minima / maxima is at
0.5
59
if g is negative
forwards reaction is spontaneous
60
enthalpy for liquid mixing
is not 0 in real solutions. all bonds and breaking bonds is enthalpically equal
61
exothermic mixing causes
explosions
62
at any temperature
vapor pressures exists
63
endothermic mixing
cool mixing or immiscible
64
knowing vapor pressure is important for
perfume , alcohol production
65
raoults law
at high concentration, liquids act ideally
66
does raoults law work for low concs
if solvent is similiar
67
henry law
low concentrations
solute behaves ideally when it is mainly surrounded by solvent molecules.
68
do many liquids obey raoult/henry
no, just similar ones
69
Positive Deviations
The A-B intermolecular interactions are weak or unfavourable compared to A-A or B-B.
Molecules prefer to be apart, not mixed.
So they separate (vaporise) earlier than expected.
Examples: propanone + CS2, water + dioxane
69
Negative Deviations
The A-B intermolecular interactions are strong or favourable compared to A-A or B-B.
Molecules prefer to be mixed, not apart.
So they separate (vaporise) later than expected.
Examples: acetone + CHCl3 (because the mixture can form H-bonds but the separate liquids cannot).
70
collagiative qualities
characteristics based on the number/ moles of x, present E.G osmosis
71
osmosis
Osmosis is diffusion of a solvent (usually water) from a dilute solution into a more concentrated one, through a semi-permeable membrane.
72
osmosis is
entropic
73
how to prevent osmosis
applying external/ osmositic pressure
74
how to measure osmostic pressure
osomoter
75
melting and boiling points are
colligative properties
76
impure substances
have higher boiling points and lower freezing points
77
chemical potentials get lower when
solutes are added
78
solid and gaseous phases
remain constant
79
why does the liquid phase change
entropy increase
80
what does paulings rule achieve to maintain
minises/reduce like ion interaction and increase opposite ion attraction for stable crystal.
81
what is the distance between cation-anions considered as?
the ionic radii sum.
82
rule 1 - pauling
A coordination polyhedron of anions is formed around every cation (and vice-versa) - it will only be stable if the cation is in contact with each of its neighbours.
83
what are Ionic crystals
linked polyhedra sets
84
radius lower limt
(r2 + r1)2 = r1 2 + r1 2
85
radius ratio
r2/r1
86
EBS, rule 2 paulings
cation charge / number of anion bonded to it
87
find the anion charge from rule 2
sum of
cation charge / number of anion interaction
88
goal of rule 2?
Rule 2 allows us to define the IDEAL structural arrangement of a crystal
89
what is a feature of a stable ionic structure
the charge on an ion is balanced by the sum of electrostatic bond strengths to the ions in its coordination polyhedron
90
lattice enthalphy of dissociation
this is the standard molar enthalphy to dissociate a solid crystal into its gaseous ion
91
what is the madlung constant?
this is the electrostatic contribution in a lattice based from distance
92
what is a Schottky Defect
a defect where two vacant sites are present. one anion, one cation site
93
what is a Frenkel Defect
defect where one site is vacant. the ion sits interstitial
94
describe ion migration for Frenkel Defects
Direct Interstitial Jump
Interstitialcy Mechanism
95
describe ion migration for Schottky Defects
To get across the unit cell into the vacancy in this a crystal, the Na+ ion must hop through the center of the cube where it squeezes past 4 Cl- and 2 Na+.
96
what determines ease of migration?
The energy of this “transition state” will determine the ease of migration.
97
why do even perfect crystals have defects
there is an equilibrium for it.
98
defects can produce...
colour centres
farbencentres
99
how do colour centres produce color?
An F-centre can be formed by X-Ray bombardment ionizing Na at the crystal surface, giving rise to electrons which diffuse into the crystal and occupy vacant anion sites.
100
how do electrons behave in the vacant site
particle in a box with allowed energies
the allowed energies may relate to the visible light region
101
how does radioactive decay produce frenkel defects?
The recoiling nucleus produces ionisation and displacement of surrounding atoms
102
what is wigners energy?
atom movement includes breaking and making bonds. Because the atom is moving from an internal site (e.g. 6 bonds) to an external site (e.g. 3 bonds), this is an endothermic process.this means that for atoms hopping back into the crystal lattice, it is an exothermic process
103
what are the pros and cons to the free model for metals
Can use the “particle in the box” model
cannot explain insulators and semiconductors.
104
what is a band
this includes all mo orbitals from the lowest energy, bonding to antibonding , the highest.
105
what is in a band
a continuous range of energies.
106
why is lithium a metal?
- half on the conductive band is filled, there is not much significant energy difference between homo and lumo so electrons can be promoted to empty orbitals, this allows for electron conductivity
107
fermi level
Energy of highest occupied molecular orbital – the HOMO
108
valence band
bottom
109
conductive band
top
110
why is nacl a conductor
filled valence band , cl 3p
empty conductive band, na 3s
large band gap - too high to promote electrons.
111
semiconductors are important as
conductivity can be controlled , great for technology
112
semiconductors
As the temperature is increased electrons are excited from the valence band to the conduction band.
113
what makes lithium a metal?
The 2s orbitals overlap to form a band. Just as the 2s orbitals in the Li atom is half-full, in the solid the 2s band is half-full – thus we have a metal.
114
what makes magnesium a metal?
3s and 3p orbitals are close in energy for Mg (recall general periodic trends in orbital energies). So the 3s and 3p bands overlap and the result is a partially filled s-p band.
115
why at high pressure, everything is a metal?
orbitals overlap, and are partially filled in the conductive band.
116
what is proof that light is a wavelength?
diffraction and inference
117
what is diffractions?
Diffraction is the spreading out of
waves when they pass through a gap
in a barrier. The gap in the barrier must be of similar size to the wavelength of the wave.
118
photoelectric effect
when UV light falls on a clean alkali metal surface, electrons are emitted with a range of KEs. there is a mininum threshold for frequency
119
what is light?
Light consists of oscillating electric and
magnetic fields that travel with speed
120
how does kinetic effect the wavelength?
Large KE causes a large momentum but small wavelength
121
atoms can
defract
122
schodinger equation is only used for
one-electron atoms
123
what does schodinger equation explain
the wave properties of atom
124
the born interpretation
The Born interpretation is based on the probability of an electron being at a particular place
125
what is the square of the wavefunction?
the square of the orbital wavefunction gives the electron density at any
location (x,y,z):
126
what are the 4 quantum numbers?
n = size and energy
l = shape
ml= orientation
ms = spin
127
wavefunctions
The wavefunction () describes the properties of an electron, atom or
molecule such as its motion
128
the Born interpretation:
the probability of finding the
particle in a small region centred at a
location.
129
wavelike properties and uncertainty
cannot say exactly where an electron
(or other particle) is when it is moving. heisenberg principle
130
if the momentum is known...
the position is unknown
131
if the position id known...
the momentum is unknown
132
what shows energy quantisation
the particle in box theory
133
if the potenial energy is high
electron would not be found there
134
the lowest energy in particle of a box is
1
135
what is requirements for particle in the box?
* The de Broglie wavelength for the particle must fit inside the box.
* The particle cannot be inside the walls (zero probability) so 2=0 in the
walls. Thus at x=0 and x=L, we know =0.
136
translational energy is ....
continous
137
describe degrees of freedom
all things can translate in 3 dimensions
linear molecule can rotate around 2 perpendicular axes, so has 2 rotational degrees of
freedom.
138
Hot band
(v=1 → v=2) Weak – very few
139
Overtone band
(v=0 → v=2) Weak - breaks v = 1 selection rule*
140
Fundamental band
(v=0 → v=1) Strong - obeys v = 1 selection rule
141
centrifugal distortion
As molecules rotate faster, their bonds stretch slightly
142
what is quantum tunneling?
small molecules can react even if they are below the activation energy. this is because they have more wavelike qualities their wavefunctions decay inside the energy barrier, but can
penetrate to the other side.
143
Quantum tunneling explains that
reactions that occur at very low temperature
144
* Lyman series
ultraviolet
145
* Balmer series
visible
146
The lyman and balmer series shows
energy release from n = 1 or 2
balmer = 2
lyman = 1
147
laporte selection rule
electrons can transition across orbital when l = 1 +-
148
The Franck-Condon principle
The strongest transitions (the most
intense in the spectrum) are to
vibrational levels in the excited state
whose wavefunctions have the
greatest overlap with the ground state
vibrational wavefunction.
149
nuclei and electrons
vertical transitions can only occur, nuclei do not move , but electrons do.
150
uv , visible light
visible light - lower energy
uv - higher energy
151
name the types of emission of a photon
non- radiative and radiative
152
radiative photon emmission
fluorescence and phosphoresce (triplets)
153
Phosphorescence
Phosphorescence is typically at longer
wavelength than fluorescence.
154
what is kasha rule?
emission occurs must from the
lowest excited state of a given electronic spin
(i.e. from S1 or T1)
155
Non-radiative relaxation
internal conversion (IC) or Intersystem crossing (ISC) –
156
Intersystem crossing (ISC) –
spin change
157
internal crossing (IC) –
no spin change
158
Intermolecular interactions
* Charges on ions (atomic or molecular ions)
* Polarity of molecules (dipoles, quadrupoles,…)
* Polarizability of molecules
* Fluctuating charge in molecules (giving dispersion forces)
159
what is hydrogen bonds?
Donation from the H-bond acceptor X lone pair into the donor Y−H sigma* orbital also contributes to weaken the Y−H bond.
