Unit 1 Flashcards
1
Q
What is the electromagnetic spectrum
A
The electromagnetic spectrum is a full range of electromagnetic radiation which travels through space with a velocity of 3x10^8ms-1 ordered by wavelength
2
Q
The relationship between wavelength and frequency formula
A
c = f λ
3
Q
What is frequency
A
Frequency is defined as the number of waves that pass of fix point in one second (Hz)
4
Q
Wavelength
A
Wavelength is the distance between two adjacent wave crests or troughs
5
Q
Wave number
A
We’ve number is the number of waves found in a certain length
ṽ = 1/λ
6
Q
Planks constant
A
6.63 x 10-34 Js
7
Q
Energy given by one mole of photons formula
A
E = Lhf
E = Lhc/λ
8
Q
Energy given by 1 photon formula
A
E = hf
E = hc/λ
9
Q
What happens when a photon is absorbed/emitted
A
When a photon is absorbed/emitted energy is gained/lost by electrons within the substance. Photons with higher frequencies can transfer greater amounts of energy than low frequency radiation
10
Q
EMS high frequency to low frequency
A
ROYGBIV (violet highest wavelength)
GAMMA, X-ray, UV, VISIBLE, INFRARED,MICROWAVE, RADIO
11
Q
Dual nature of radiation
A
EM radiation has a dual nature and can be described as a wave and as a particle.
12
Q
What happens when energy is transferred to atoms
A
Electrons within the atom are promoted to a higher energy level. When the excited electrons fall back to the original, ground state, energy level then release this fixed quantity of energy in the form of a photon (this is called a quanta).
High temperatures are used to excite electrons within atoms.
13
Q
Describe an emission spectrum of a sample
A
An emission spectrum of a sample is produced by measuring the intensity of light emitted at different wavelength. The spectrum of emitted light is not continuous, but is a series of lines at specific frequencies.
14
Q
How is absorption spectra produced
A
When a beam of continuous radiation is directed through a gaseous sample, it can cause an atom to make transition from its ground state to an excited state. If the frequency of light, and therefore the energy of a photon, corresponds to an excitation energy of an atom, then the photon of light is absorbed.
The radiation that emerges were therefore have certain wavelengths missing.
These show up as dark lines on a continuous spectrum called an atomic absorption spectrum.
15
Q
What excites atoms in emission spectroscopy
A
Heat or electricity
The electrons within the atoms are promoted and as they drop to lower energy levels (not necessarily the ground state) they emit photons.
16
Q
How can the discrete lines in the emission or absorption spectra be explained?
A
Electrons can display particle and wave properties. Within the atom, electrons behave like waves.
17
Q
What are the different sizes and shapes of waves possible around the nucleus called and how many electrons can each contain
A
They’re called orbitals and hold a maximum of two electrons
18
Q
How do electrons behave in an atom
A
Electrons behave a standing (stationary) waves in an atom which are waves that vibrate in time but do not move in space.
19
Q
Heisenbergs uncertainty principle
A
“It is impossible to define the position and momentum of an electron with absolute precision”
20
Q
How can an orbital be defined
A
An orbital can be defined as an area of space that has a 90% likelihood of containing an electron
21
Q
What are the fixed amount of energy in electrons called
A
Every electron in an atom have fixed amount of energy called quanta and therefore can be defined by a set of four numbers called quantum numbers
22
Q
Quantum number one – principal quantum number
A
Symbol: n
The principal quantum number tells us the main energy level the electron is on and will have a value of 1,2,3…..
23
Q
Quantum number two – angular momentum number
A
Symbol: l
Formula: l=n-1
The emission spectra shows doublets and triplets which tells us the energy levels are split into subshells
24
Q
Quantum number two - corresponding letters in shapes
A
l=0 letter=s
l=1 letter=p
l=2 letter=d
l=3 letter=f
25
What is the maximum number of electrons in S orbital can contain
2
26
Max number of electrons are p orbital can contain
6
27
Max number of electrons d orbital contain
10
28
Quantum number three – magnetic quantum number
Symbol: ml (subscript l)
This determines the orientation of the orbitals in space. It can take the value of +/- l
I.E. if l=1 then can be -1,0,+1
29
Describe the energy in orbitals
Degenerate which means they have equal energy and the electrons have an equal likelihood of going into each orbital
30
Pauli exclusion principle
“ no two electrons in one atom can I have the same set of four quantum numbers”
31
Describe the spin of electrons in orbitals
Two electrons are in the same orbital they must have opposite spins
32
Quantum number four – spin magnetic quantum number
Symbol: ms (subscript s)
This determine the direction of spin and has a value of +/- 1/2
33
Aufbau Principle
“ electrons fill orbitals in order of increasing energy”
34
Hund’s Rule
“ when degenerate orbitals are available, electrons fill each singly, keeping their spins parallel before spin pairing stars”
35
Describe the noble gases P orbital
All noble gases have a filled p-orbital in their outer shell so are stable
36
Describe the energy required to remove electrons from filled orbitals, half filled orbitals, partly filled orbitals
Filled orbitals require the most energy
Half filled orbitals require more energy than partly filled orbitals
Part filled orbitals requires the least amount of energy
37
What are the elements that are the transition metal anomalies
Chromium Cr
Copper Cu
38
Cr configuration
1s2 2s2 2p6 3s2 3p6 4s1 3d5
39
Cu configuration
1s2 2s2 2p6 3s2 3p6 4s1 3d10
40
The principle of VSEPR
VALENCE SHELL ELECTRON PAIR REPULSION
Electron pairs are negatively charged. If you’re trying to bring them close together they will repel as far away from each other as possible. This means that electron pair is arranged to minimise repulsion and maximise separation so the shapes of molecules can be predicted if you know the number of bonded and lone pairs of electrons around a central atom.
41
Calculating number of bonded and unbounded pairs of electrons around a central atom (VSEPR)
Take the number of outer electrons of the central atom an answer that one electron for each surrounding atom.
If there is an overall -1 charge then add another electron.
If there is an overall +1 charge then minus 1 electron.
42
6 electron pairs shape name
Octahedral
43
2 electron pairs arrangement
Linear
44
3 electron pairs arrangement
Trigonal planar
45
4 electron pairs arrangement
Tetrahedral
46
5 electron pairs arrangement
Trigonal bipyramidal
47
6 electron pairs arrangement
Octahedral
48
What a lone/non-bonding electron pairs cause cause
Will cause a greater electron repulsion so the bond angles will be reduced if there are more lone pairs
49
What is a dative covalent bond
When both electrons in the bond are supplied by one of the atoms
50
Transition metal definition
Metals with an incomplete d sub shell in at least one of their ions
51
Things to remember for transition metals
4s electrons are lost 1st to make ions
Cr and Cu have special electron arrangement due to stability factors
52
When are elements in an oxidation state
Elements are said to be in particular oxidation states when they have a specific oxidation number.
53
Transition metals oxidation states
Transition metals have variable oxidation states
54
Calculating transition metal oxidation state
- free (uncombined) elements have an oxidation number = 0
- Ions containing single atoms have an oxidation number of that is the same as the charge on the ion
- most compounds oxygen oxidation number (usually) = -2
- most compounds hydrogen oxidation number (usually) = +1
- The sum of all the oxidation numbers of all the atoms in a molecule or neutral ion must add up to 0.
- The sum of all the oxidation numbers of all the atoms in a polyatomic ion must be equal to the charge on the ion
55
Poly atomic ion
Ion with 2 or more elements
?
56
Ligands
Ligands are molecules or negative ions with at least one lone pair of electrons (or negative charge) which can be donated to the central metal atom or ion to form a bond. This will be a dative bond.
Molecules or negative ions that bond to the central metal atom or ion in a complex
57
How do ligands tend to be distributed
Ligands tend to be distributed octahedrally around the central metal atom/ion which gives them a coordination number of six
But other arrangements are possible
58
Coordination number
The coordination number is the number of bonds from the central metal atom ion to the ligands
59
Naming complexes
1. The number and name of the ligand(s) comes first
2. Central atom/ion name comes second
3. Roman numerals show oxidation state of the central atom/ion
4. Complex negative ions end in -ate
5. If there are 2 or more ligands their names alphabetically (however when writing the FORMULA the ligands are listed alphabetically by symbol)
60
Cobalt ions names
Positive: cobalt
Negative: cobaltate
61
Aluminium ions names
Positive: aluminium
Negative: aluminate
62
Vanadium ions names
Positive: vanadium
Negative: vanadate
63
Copper ions names
Positive: copper
Negative: cuprate
64
Iron ions names
Positive: iron
Negative: ferrate
65
Common ligands names - water
Aquo
66
Common ligands names - ammonia
Ammine
67
Common ligands names - hydroxide
Hydroxido
68
Common ligands names - cyanide
Cyanido
69
Common ligands names - chloride
Chlorido
70
Common ligands names - fluoride
Fluorido
71
Common ligands names - oxalate
Oxalato
72
List the possible d orbitals in octahedral complexes
d xy
d yz
d xz
d x2-y2
d z2
73
Describe the difference in repulsion in d orbital octahedral complexes
If the d electrons are located in either the dz2 or dx2-y2 orbitals then they will repel the ligands whereas if they are located in the dxy, dxz or dyz orbitals there will be less repulsion
74
In octahedral complex is in d orbitals where are the first six electrons found
As a result of the different energy states between the orbitals the first six electrons will be found in the t2g orbitals in the next four in the eg orbitals.
75
What does the 🔺E depend on in octahedral complex of d orbitals
The 🔺E depends on the ligands attached to the central atom/ion.
If the ligands cause a large difference in energy they are known as strong field ligand, whereas if they called a small difference in energy they are known as a weak field Ligands.
76
What are ligands that cause a large difference in energy called
Ligands that cause a large difference in energy are known as strong field ligand
77
What are ligands that cause a small difference in energy called
Ligands that cause a small difference in energy are known as weak field ligands.
78
The spectrochemical series in order from weak field to strong field ligands
I- < Br- < Cl- , H20 < NH3 < CN-
79
What happens when a d electron absorbs sufficient energy
If a d electron in a low energy orbital (t2g) absorbs enough energy that can be promoted to an excited state (eg).
If this energy comes from the visible part of the spectrum this will result in the compound being the complementary colour
80
What happens when there’s more than one electron to promote
If there is more than one electron to promote, multiple wavelengths can be absorbed
81
What happens when ligands are changed
When ligands are changed the d-d splitting changes sort the wavelengths absorbed to promote electrons change which changes the colour of the complex .
82
What does UV and visible absorption spectroscopy involve
UV and visible absorption spectroscopy involves transitions between electron energy levels (previously mentioned) in atoms and molecules where the energy difference corresponds to UV or visible frequencies
83
Approx UV wavelength
200nm - 400nm
84
Approx visible wavelength
400nm - 700nm
85
What is thought about the unpaired d-electrons or infilled d-orbitals allow
It is believed that the presence of unpaired d electrons or infilled d orbitals
allows intermediate complexes to form, providing reaction pathways of lower energy compared to the uncatalysed reaction.
This gives rise to heterogeneous catalysis.
86
What are heterogenous catalysis
Catalysts in a different state from the reactants
87
What are homogeneous catalysis
Catalysts in the same state as the reactants
88
What is thought to play an important part in homogeneous catalysis
Variable oxidation states of transition metals
89
Stoichiometry
Stoichiometry looks at the ‘amount’ of matter present in a substance. It is the study of the mole relationships involved in chemical reactions.
90
Compare actual yields and theoretical yield
Actual yields will always be less than theoretical yield
91
Why will the actual yield always be less than the theoretical yield
Mass transfer or mechanical losses
Purification of products
Sage reactions occurring
Equilibrium positions
92
Quantitative reactions
They use balance equations and are reactions in which the reactants react completely according to the balanced equation
93
Gravimetric analysis
Used to determine the mass of an element or compound in a substance
94
How does gravimetric analysis work
To determine the mass of an element or compound in a substance, the substance is converted into another substance of known chemical composition, which can be isolated and purified
95
Gravimetric analysis methods of isolating and purifying
Precipitation
Volatilisation
96
Precipitation
Can isolate the solid that is formed by filtration which can then be purified.
The filtrate can then be tested to ensure the reaction has gone to completion by adding a few more drops of the other reactant to ensure no more precipitate is formed. The precipitate can then be washed and dried to a constant mass and weighed.
97
Volatilisation
Liquids of different boiling points can easily be separated by distillation. Then the products can be purified.
The initial substance is heated and any volatile products evaporate. Substance is initially wait and then heated to a constant Mass. Final mass of the product is then recorded.
98
Process of heating to a constant mass
- take the initial mass of the substance
- heat the substance
- allow the substance to cool in a desiccator to prevent absorption of water
- weighing
- repeat this process of heating and cooling until no further change in mass is observed
99
Equilibrium
Reaction is equilibrium when the rate of the forward and reverse reactions are exactly the same AND the concentration of products and reactants remain constant but really equal
100
What happens as the value of K increases
The higher the values of K the more the products side is favoured
101
K = 1 x 10-3
Effectively no reaction (mainly reactants in the mixture)
102
K = 1 x 10^3
Reaction is effectively complete
103
K between the values of 1 x 10-3 and 1x10^3
Reaction is at equilibrium
104
K > 1
More products than reactants
105
K < 1
More reactants than products
106
K = 1
Equal amounts of products and reactants
107
Equilibrium - what are all pure solids and liquids assign the value of
1
108
Partial pressure
A partial pressure is the pressure that the gas would exert if it were on its own and not part of the gas mix
109
Le Chatelier’s Principle
“ when our reaction at equilibrium is subject to change, the composition altars in such a way as to minimise the effects of that change”
110
Concentration affect of K
Concentration alters the composition of the equilibrium mixture.
As increasing the concentration of the reactants will favour the forward reaction, to re-establish the equilibrium this will result in a rise in both products and reactants concentrations.
NO OVERALL EFFECT ON K
111
Pressure affect of K
No overall effect on K
112
Catalyst effect on K
Adding a catalyst will increase the rate of the forward and back reactions by the same degree meaning that the equilibrium will be reached quicker but the value of K will be unaffected.
NO OVERALL EFFECT ON K
113
Temperature affect on K
Temperature is a measure of energy. Increasing temperature have a favourite the Endo thermic reaction and therefore very the concentration of the reactants/product mix significantly.
TEMPERATURE AFFECTS K
114
Temperature and endothermic reactions
Increasing temperature favours endothermic reactions.
115
Temperature and exothermic reactions
Decreasing temperature favours exothermic reactions
116
Brønsted-Lowry definition of an acid
Acid is a proton donor
117
Brønsted-Lowry definition of a base
A base is a proton acceptor
118
What does every acid form
Conjugate base formed by the loss of a proton
119
What does every base form
Conjugate acid formed by gain of a proton
120
Water dissociation - What happens when water is repeatedly purified
When water is purified by repeated distillation the conductivity will reach a point where it becomes constant.
Even the purest water conduct a little which proves that water contains ions.
121
What term is used to describe water
Amphoteric - can act as an acid or a base
122
Ionic product of water value
At 298K = 1 x 10^14 mol2l2
123
Ionic product of water symbol
Kw
(Subscript w)
124
How does the ionic product of water vary
Temperature
As temperature increases Kw increases
125
Strong acid/base definition
A strong acid/base is defined as an acid/base that completely dissociates in water.
This means that ALL the molecules/lattices break up to form ions.
(Solid arrow is used)
126
Strong acids
Hydrochloric acid (HCl)
Sulphuric acid (H2SO4)
Nitric acid (HNO3)
127
Strong bases
Sodium hydroxide (NaOH)
Potassium hydroxide (KOH)
Calcium hydroxide Ca(OH)2
128
Weak acid/base definition
A weak acid/base is defined as an acid/base that only partially dissociate in water.
This means that only some of the molecules form ions.
129
Weak acids
Carboxylic acids
Carbonic acid (H2CO3)
Sulphurous acid (H2SO3)
130
Weak bases
Ammonia (NH3)
Ammonium hydroxide (NH4OH)
Amines
131
Equimolar meaning
Same number of moles
132
Equimolar solutions of strong and weak acids
Have different pH values but the stoichiometry of the reactions are the same
133
Rate, conduction, titration of strong acids/bases compared to weak
Rate = faster
Conduction = higher
Titration = same
134
Rate, conduction, titration of weak acids/bases compared to strong
Rate = slower
Conduction = lower
Titration = same
135
Why is the rate of strong acid/bases faster than weak
There are more free ions in the strong acid/base for collisions to occur, therefore more successful collisions, therefore a faster rate.
The weak acid/base would react with the three ions than the equilibrium would move to the left to create more therefore re-establish the K value
136
Why is the conduction of strong acid/bases higher than weak
Have more ions that are free to move so conduct better
137
Titration simple explanation
As an acid is added to an alkali (or vice versa) it is neutralised.
H+(aq) + OH-(aq) ——> H2O (l)
138
Titration of strong acid /base
For the strong acid/base titration/neutralisation will continue until all free ions are used up.
139
Titration of weak acid/base
The ions will be used and as this occurs the dissociation equilibrium of the acid/base move to the left to break up more molecules/lattices to replace the ions. This will continue until all molecules/lattices are broken up.
140
What is the result of a titration of the concentrations of the strong and the weak solution are the same
If the concentrations of the strong and the Wieck solution are the same then they have the ability to make the same concentration of ions therefore they will yield the same titration result
141
What determines the pH of the salt produced
The strength of the acid and a base used in the neutralisation and the equivalence point of the neutralisation
142
Equivalence point
The point at which the reaction has just finished
143
Endpoint
The endpoint is where a noticeable change occurs
144
Strong acid strong base salt
Neutral salt
145
Strong acid/week base salt
Acidic salt
146
Weak acid/strong base salt
Basic salt
147
Weak acid/weak base salt
Cannot predict without more information
148
What are soaps an example of
Sort are examples of weak acids (fatty acids) + strong base (NaOH) so are there for alkaline salts
149
Acid dissociation constant
Symbol: Ka (subscript a)
The stronger the acid the higher degree of dissociation so the higher the value for Ka
150
pH of weak acids formula
pKa = -log10Ka
151
Acid dissociation formula
Ka = [H3O+][A-] / [HA]
(Products over reactants)
Pure solids and liquids given value of 1
152
Buffer solution
A buffer solution is a solution in which the pH remained approximately constant, even with additions of small volumes of acid or base.
153
What makes an acidic buffer
Weak acid + one of its salt made from a strong base
154
What makes an alkaline buffer
Weak base + one of its salts made from a strong acid
155
1st law of thermodynamics
Energy is conserved. Energy cannot be created or destroyed, it can only be changed from one form to another
156
Hess’ law
Hess’ law states that the enthalpy change for a reaction depends on the initial and final stage of the reaction and is independent of the root the reaction takes.
This means that no matter the route taken, the enthalpy change will always be the same for a reaction.
157
Enthalpy of formation
The enthalpy change when ONE MOLE of a substance is formed from its elements in their standard state
158
What temperature are reactants and products in the standard state
298K
159
Define standard state
The most stable state at room temperature and pressure
160
Standard pressure and temperature
298K
1 atm
161
Midpoint of colour change
[In-] = [HIn]
162
When is the colour change distinguishable
The colour changes only distinguishable when [HIn] and [In-] differ by a factor of 10
163
Range in which an indicator changes colour
pH = pKIn +/- 1
(Subscript In)
164
Who are indicators chosen
Indicators are chosen so that the colour change occurs with addition of one drop.
It should be chosen to change colour at the equivalence point of the reaction.
165
What is entropy (S)
The entropy (S) of a system is a measure of the degree of disorder. The greater the degree of disorder, the greater the entropy.
166
Second law of thermodynamics
The total entropy of a reaction system for any reaction system and its surroundings always increases for a spontaneous reaction. It is the law of increasing disorder (entropy).
167
Degree of disorder and state
Solids are the most ordered state of matter so have the lowest entropy values.
Gases have the highest degree of disorder, so have the highest entropy values
168
The effect of increasing temperature on disorder
Increasing temperature increase is disorder
Increasing temperature increases entropy
(Think of it as going from solid liquid gas)
169
What happens to entropy as a substance melts or boils
Rapid increase in entropy as a substance melts. Even more rapid increase in entropy when a substance boils
170
Third law of thermodynamics
The entropy of a perfect Crystal at absolute zero (0K) is zero. This means that all motion of the particles within the crystal stops.
171
What is the standard entropy of a substance
The entropy value for the substance in its standard state
172
Entropy change for a system at equilibrium
Will be zero as the amount of disorder remains unchanged
173
Gibbs free energy
The energy released by chemical reactions can be used to ‘do work’ which is classed as free energy.
The total energy released by a chemical reaction is not all free energy as some of this energy will go into the surroundings.
174
Favourable conditions for a reaction
🔺H should be negative
🔺S should be positive
🔺G should be negative to show a release in energy
175
Free energy (G) calculation
🔺G* = 🔺H* - T🔺S*
176
🔺G negative
Indicates that a reaction may occur and the reaction is classed as feasible, as the equilibrium position favours a product.
However doesn’t give an indication of the rate of reaction
177
Applying the concept of free energy understand of conditions
🔺G* it’s a free energy change for the reaction at standard temperature and pressure using 1mol.
This is a measure of the maximum amount of work available from a system
178
When will a reaction process
Provided 🔺G* is negative
If the value is positive this does not mean that the reaction will not take place, it just means that the reactants are favoured
179
Applying the concept of free energy under non-standard conditions
Once a reaction begins we no longer have standard conditions (either the temperature, concentration or pressure or change away from standard values.
This means that it is important to consider non-standard conditions
180
What is the state that controls the rate of reaction called
Rate determining step (r.d.s.) I will be the slowest step in the reaction as a reaction cannot go any faster than its slowest step.
181
How can order of reaction be determined
The order of a reaction can only be determined experimentally as reactions may go through a series of steps called the reaction mechanism
182
How does rate (k) vary
Temperature
Particle size
Addition of catalysts
The rate constant for first order reactions DO NOT VARY with concentration. All other order reactions do vary with concentration
In zero order reactions the rate is constant
183
Common ligands name - carbon monoxide
Carbonyl
