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moad Flashcards

1
Q

closed system

A

heat can exchange, not material

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2
Q

isolated system

A

heat nor material can be exchange with its surroundings

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3
Q

energy

A

work capacity

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4
Q

work

A

change in molecular motion in a uniform way.

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5
Q

heat

A

change in molecular motion in a chaotic way

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6
Q

adiabatic

A

heat cannot be exchange with the environment, temperature changes

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7
Q

isothermal

A

heat can be exchange with the environment, and temperature remains constant, in a water bath

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8
Q

heat is

A

irreversible

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9
Q

work is

A

reversible

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10
Q

heat and work are

A

path functions

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11
Q

state functions state that

A

path is not important

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12
Q

internal energy

A

state function were KE + PE

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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

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14
Q

1st law

A

for an isolated system, energy is constant

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15
Q

Show the 1st law as a formula

A

delta U = q + w

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16
Q

What does applying heat does to the population levels

A

-same seperation
- different population

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17
Q

cp mean

A

constant pressure

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18
Q

constant pressure for chemist is…

A

important

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19
Q

what is the definition of heat capacity

A

heat capacity is the ability to raise the temperature by 1k

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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.

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21
Q

enthalpy

A

heat change at constant pressure

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22
Q

isobaric

A

same

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23
Q

solids and liquids take up

A

little volume , therefore little volume change occcurs at these states

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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

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25
Q

what happens during expansions?

A

the seperation between energy levels decreases. in uniform reversible expansion it is repopulated in scale according to boltzmann

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26
Q

what happens to the energy levels in adiabatic reversible expansion

A

energy levels seperation decrease, but population is constant/ equilibrate
this shows temperature decrease

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27
Q

Hess law

A

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

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28
Q

heat capacity changes for

A

each temperature

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29
Q

more work is done for cp than cv why so

A

force pushing to increase volume
bond stretches

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30
Q

Spontaneous reactions are

A

irreversible and do not need any interventions

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31
Q

what happens to entropy of the universe during a spontaneous reaction

A

it increases, to reverse the reaction requires a lost of entropy of the universe which is against the 1st law

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32
Q

2nd law

A

energy spontaneously tends to moves from a highly concentrated region and diffuses and spreads out

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33
Q

how is chaos prevented

A

activation energies
being delayed/ so slow

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34
Q

what is theorised

A

the end of the universe will end when there is complete disorder

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35
Q

entropy

A

energy quality that leads to spontaneous changes

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36
Q

entropy is

A

additive and a state function

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37
Q

entropy has a

A

inverse relationship between temperature. at high temperatures additional heat to system has a smaller influence to entropy

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38
Q

why is water greater than troutons law=?

A

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.

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39
Q

why is acetic acid have a lower value than troutons law?

A

this is because there is more order than expected in gaseous forms

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40
Q

entropy is a law of probability, therefore ….

A

it does not apply to large traditional size things eg the water bottle is not constantly moving

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41
Q

3rd law

A

entropy of perfect crystal is = 0

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42
Q

slow cooling

A

s =0

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43
Q

why is entropy nor 0 during fast cooling

A

molecules cool too quickly before they can rearrange themselves to the lowest energy configuration

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44
Q

h can tell if

A

reaction is exo or endothermic
endo = + exo = -

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45
Q

hemoltz value is useful for

A

scientist that use cnstant pressure, A.

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46
Q

for solids and liquids pressure and volume are

A

independant

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47
Q

for solids and liquids gibbs and pressure are almost

A

independant

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48
Q

chemical potential

A

ability to take part in chemical processes ei reactivity potential energy

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49
Q

if a gas / liquid is in equilbrium, this means that

A

g = 0
chemnical potential are same
no driving force to chzange

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50
Q

why is water gas at 120

A

lowest chemical potential at that temp.
most stable

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51
Q

gases have

A

the greatest molar entropy

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52
Q

how do ice skates work

A

temperature is constant but there is a pressure change, this causes the ice to melt to liquid phase - it crosses the solid liquid boundary

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53
Q

why does ice melt when you are standing?

A

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

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54
Q

how do pressure cookers work

A

increases the boiling point of water
food can cook at higher temperatures

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55
Q

gibbs free energy relies on

A

amount of substance/ moles

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56
Q

ideal gas

A

no chemical reactions

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57
Q

why is enthalpy 0 is ideal mixing

A

no bonds or reaction takes place purely entropic.

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58
Q

for mixing minima / maxima is at

A

0.5

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59
Q

if g is negative

A

forwards reaction is spontaneous

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60
Q

enthalpy for liquid mixing

A

is not 0 in real solutions. all bonds and breaking bonds is enthalpically equal

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61
Q

exothermic mixing causes

A

explosions

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62
Q

at any temperature

A

vapor pressures exists

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63
Q

endothermic mixing

A

cool mixing or immiscible

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64
Q

knowing vapor pressure is important for

A

perfume , alcohol production

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65
Q

raoults law

A

at high concentration, liquids act ideally

66
Q

does raoults law work for low concs

A

if solvent is similiar

67
Q

henry law

A

low concentrations
solute behaves ideally when it is mainly surrounded by solvent molecules.

68
Q

do many liquids obey raoult/henry

A

no, just similar ones

69
Q

Positive Deviations

A

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
Q

Negative Deviations

A

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
Q

collagiative qualities

A

characteristics based on the number/ moles of x, present E.G osmosis

71
Q

osmosis

A

Osmosis is diffusion of a solvent (usually water) from a dilute solution into a more concentrated one, through a semi-permeable membrane.

72
Q

osmosis is

A

entropic

73
Q

how to prevent osmosis

A

applying external/ osmositic pressure

74
Q

how to measure osmostic pressure

A

osomoter

75
Q

melting and boiling points are

A

colligative properties

76
Q

impure substances

A

have higher boiling points and lower freezing points

77
Q

chemical potentials get lower when

A

solutes are added

78
Q

solid and gaseous phases

A

remain constant

79
Q

why does the liquid phase change

A

entropy increase

80
Q

what does paulings rule achieve to maintain

A

minises/reduce like ion interaction and increase opposite ion attraction for stable crystal.

81
Q

what is the distance between cation-anions considered as?

A

the ionic radii sum.

82
Q

rule 1 - pauling

A

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
Q

what are Ionic crystals

A

linked polyhedra sets

84
Q

radius lower limt

A

(r2 + r1)2 = r1 2 + r1 2

85
Q

radius ratio

A

r2/r1

86
Q

EBS, rule 2 paulings

A

cation charge / number of anion bonded to it

87
Q

find the anion charge from rule 2

A

sum of
cation charge / number of anion interaction

88
Q

goal of rule 2?

A

Rule 2 allows us to define the IDEAL structural arrangement of a crystal

89
Q

what is a feature of a stable ionic structure

A

the charge on an ion is balanced by the sum of electrostatic bond strengths to the ions in its coordination polyhedron

90
Q

lattice enthalphy of dissociation

A

this is the standard molar enthalphy to dissociate a solid crystal into its gaseous ion

91
Q

what is the madlung constant?

A

this is the electrostatic contribution in a lattice based from distance

92
Q

what is a Schottky Defect

A

a defect where two vacant sites are present. one anion, one cation site

93
Q

what is a Frenkel Defect

A

defect where one site is vacant. the ion sits interstitial

94
Q

describe ion migration for Frenkel Defects

A

Direct Interstitial Jump
Interstitialcy Mechanism

95
Q

describe ion migration for Schottky Defects

A

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
Q

what determines ease of migration?

A

The energy of this “transition state” will determine the ease of migration.

97
Q

why do even perfect crystals have defects

A

there is an equilibrium for it.

98
Q

defects can produce…

A

colour centres
farbencentres

99
Q

how do colour centres produce color?

A

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
Q

how do electrons behave in the vacant site

A

particle in a box with allowed energies
the allowed energies may relate to the visible light region

101
Q

how does radioactive decay produce frenkel defects?

A

The recoiling nucleus produces ionisation and displacement of surrounding atoms

102
Q

what is wigners energy?

A

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
Q

what are the pros and cons to the free model for metals

A

Can use the “particle in the box” model
cannot explain insulators and semiconductors.

104
Q

what is a band

A

this includes all mo orbitals from the lowest energy, bonding to antibonding , the highest.

105
Q

what is in a band

A

a continuous range of energies.

106
Q

why is lithium a metal?

A
  • 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
Q

fermi level

A

Energy of highest occupied molecular orbital – the HOMO

108
Q

valence band

A

bottom

109
Q

conductive band

A

top

110
Q

why is nacl a conductor

A

filled valence band , cl 3p
empty conductive band, na 3s
large band gap - too high to promote electrons.

111
Q

semiconductors are important as

A

conductivity can be controlled , great for technology

112
Q

semiconductors

A

As the temperature is increased electrons are excited from the valence band to the conduction band.

113
Q

what makes lithium a metal?

A

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
Q

what makes magnesium a metal?

A

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
Q

why at high pressure, everything is a metal?

A

orbitals overlap, and are partially filled in the conductive band.

116
Q

what is proof that light is a wavelength?

A

diffraction and inference

117
Q

what is diffractions?

A

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
Q

photoelectric effect

A

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
Q

what is light?

A

Light consists of oscillating electric and
magnetic fields that travel with speed

120
Q

how does kinetic effect the wavelength?

A

Large KE causes a large momentum but small wavelength

121
Q

atoms can

A

defract

122
Q

schodinger equation is only used for

A

one-electron atoms

123
Q

what does schodinger equation explain

A

the wave properties of atom

124
Q

the born interpretation

A

The Born interpretation is based on the probability of an electron being at a particular place

125
Q

what is the square of the wavefunction?

A

the square of the orbital wavefunction gives the electron density at any
location (x,y,z):

126
Q

what are the 4 quantum numbers?

A

n = size and energy
l = shape
ml= orientation
ms = spin

127
Q

wavefunctions

A

The wavefunction () describes the properties of an electron, atom or
molecule such as its motion

128
Q

the Born interpretation:

A

the probability of finding the
particle in a small region centred at a
location.

129
Q

wavelike properties and uncertainty

A

cannot say exactly where an electron
(or other particle) is when it is moving. heisenberg principle

130
Q

if the momentum is known…

A

the position is unknown

131
Q

if the position id known…

A

the momentum is unknown

132
Q

what shows energy quantisation

A

the particle in box theory

133
Q

if the potenial energy is high

A

electron would not be found there

134
Q

the lowest energy in particle of a box is

A

1

135
Q

what is requirements for particle in the box?

A
  • 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
Q

translational energy is ….

A

continous

137
Q

describe degrees of freedom

A

all things can translate in 3 dimensions

linear molecule can rotate around 2 perpendicular axes, so has 2 rotational degrees of
freedom.

138
Q

Hot band

A

(v=1 → v=2) Weak – very few

139
Q

Overtone band

A

(v=0 → v=2) Weak - breaks v = 1 selection rule*

140
Q

Fundamental band

A

(v=0 → v=1) Strong - obeys v = 1 selection rule

141
Q

centrifugal distortion

A

As molecules rotate faster, their bonds stretch slightly

142
Q

what is quantum tunneling?

A

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
Q

Quantum tunneling explains that

A

reactions that occur at very low temperature

144
Q
  • Lyman series
A

ultraviolet

145
Q
  • Balmer series
A

visible

146
Q

The lyman and balmer series shows

A

energy release from n = 1 or 2
balmer = 2
lyman = 1

147
Q

laporte selection rule

A

electrons can transition across orbital when l = 1 +-

148
Q

The Franck-Condon principle

A

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
Q

nuclei and electrons

A

vertical transitions can only occur, nuclei do not move , but electrons do.

150
Q

uv , visible light

A

visible light - lower energy
uv - higher energy

151
Q

name the types of emission of a photon

A

non- radiative and radiative

152
Q

radiative photon emmission

A

fluorescence and phosphoresce (triplets)

153
Q

Phosphorescence

A

Phosphorescence is typically at longer
wavelength than fluorescence.

154
Q

what is kasha rule?

A

emission occurs must from the
lowest excited state of a given electronic spin
(i.e. from S1 or T1)

155
Q

Non-radiative relaxation

A

internal conversion (IC) or Intersystem crossing (ISC) –

156
Q

Intersystem crossing (ISC) –

A

spin change

157
Q

internal crossing (IC) –

A

no spin change

158
Q

Intermolecular interactions

A
  • Charges on ions (atomic or molecular ions)
  • Polarity of molecules (dipoles, quadrupoles,…)
  • Polarizability of molecules
  • Fluctuating charge in molecules (giving dispersion forces)
159
Q

what is hydrogen bonds?

A

Donation from the H-bond acceptor X lone pair into the donor Y−H sigma* orbital also contributes to weaken the Y−H bond.

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