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AH Chem > Unit 1 > Flashcards

Unit 1 Flashcards

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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

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2
Q

The relationship between wavelength and frequency formula

A

c = f λ

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3
Q

What is frequency

A

Frequency is defined as the number of waves that pass of fix point in one second (Hz)

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4
Q

Wavelength

A

Wavelength is the distance between two adjacent wave crests or troughs

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5
Q

Wave number

A

We’ve number is the number of waves found in a certain length

ṽ = 1/λ

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6
Q

Planks constant

A

6.63 x 10-34 Js

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7
Q

Energy given by one mole of photons formula

A

E = Lhf

E = Lhc/λ

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8
Q

Energy given by 1 photon formula

A

E = hf

E = hc/λ

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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

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10
Q

EMS high frequency to low frequency

A

ROYGBIV (violet highest wavelength)

GAMMA, X-ray, UV, VISIBLE, INFRARED,MICROWAVE, RADIO

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11
Q

Dual nature of radiation

A

EM radiation has a dual nature and can be described as a wave and as a particle.

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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.

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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.

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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.

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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.

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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.

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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

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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.

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19
Q

Heisenbergs uncertainty principle

A

“It is impossible to define the position and momentum of an electron with absolute precision”

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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

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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

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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…..

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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

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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

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25
Q

What is the maximum number of electrons in S orbital can contain

A

2

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26
Q

Max number of electrons are p orbital can contain

A

6

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27
Q

Max number of electrons d orbital contain

A

10

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28
Q

Quantum number three – magnetic quantum number

A

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

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29
Q

Describe the energy in orbitals

A

Degenerate which means they have equal energy and the electrons have an equal likelihood of going into each orbital

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30
Q

Pauli exclusion principle

A

“ no two electrons in one atom can I have the same set of four quantum numbers”

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31
Q

Describe the spin of electrons in orbitals

A

Two electrons are in the same orbital they must have opposite spins

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32
Q

Quantum number four – spin magnetic quantum number

A

Symbol: ms (subscript s)

This determine the direction of spin and has a value of +/- 1/2

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33
Q

Aufbau Principle

A

“ electrons fill orbitals in order of increasing energy”

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34
Q

Hund’s Rule

A

“ when degenerate orbitals are available, electrons fill each singly, keeping their spins parallel before spin pairing stars”

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35
Q

Describe the noble gases P orbital

A

All noble gases have a filled p-orbital in their outer shell so are stable

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36
Q

Describe the energy required to remove electrons from filled orbitals, half filled orbitals, partly filled orbitals

A

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

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37
Q

What are the elements that are the transition metal anomalies

A

Chromium Cr

Copper Cu

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38
Q

Cr configuration

A

1s2 2s2 2p6 3s2 3p6 4s1 3d5

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39
Q

Cu configuration

A

1s2 2s2 2p6 3s2 3p6 4s1 3d10

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40
Q

The principle of VSEPR

VALENCE SHELL ELECTRON PAIR REPULSION

A

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.

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41
Q

Calculating number of bonded and unbounded pairs of electrons around a central atom (VSEPR)

A

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.

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42
Q

6 electron pairs shape name

A

Octahedral

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43
Q

2 electron pairs arrangement

A

Linear

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44
Q

3 electron pairs arrangement

A

Trigonal planar

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45
Q

4 electron pairs arrangement

A

Tetrahedral

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46
Q

5 electron pairs arrangement

A

Trigonal bipyramidal

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47
Q

6 electron pairs arrangement

A

Octahedral

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48
Q

What a lone/non-bonding electron pairs cause cause

A

Will cause a greater electron repulsion so the bond angles will be reduced if there are more lone pairs

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49
Q

What is a dative covalent bond

A

When both electrons in the bond are supplied by one of the atoms

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50
Q

Transition metal definition

A

Metals with an incomplete d sub shell in at least one of their ions

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51
Q

Things to remember for transition metals

A

4s electrons are lost 1st to make ions

Cr and Cu have special electron arrangement due to stability factors

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52
Q

When are elements in an oxidation state

A

Elements are said to be in particular oxidation states when they have a specific oxidation number.

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53
Q

Transition metals oxidation states

A

Transition metals have variable oxidation states

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54
Q

Calculating transition metal oxidation state

A
  • 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
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55
Q

Poly atomic ion

A

Ion with 2 or more elements

?

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56
Q

Ligands

A

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

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57
Q

How do ligands tend to be distributed

A

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

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58
Q

Coordination number

A

The coordination number is the number of bonds from the central metal atom ion to the ligands

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59
Q

Naming complexes

A
  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)
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60
Q

Cobalt ions names

A

Positive: cobalt

Negative: cobaltate

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61
Q

Aluminium ions names

A

Positive: aluminium

Negative: aluminate

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62
Q

Vanadium ions names

A

Positive: vanadium

Negative: vanadate

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63
Q

Copper ions names

A

Positive: copper

Negative: cuprate

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64
Q

Iron ions names

A

Positive: iron

Negative: ferrate

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65
Q

Common ligands names - water

A

Aquo

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66
Q

Common ligands names - ammonia

A

Ammine

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67
Q

Common ligands names - hydroxide

A

Hydroxido

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68
Q

Common ligands names - cyanide

A

Cyanido

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69
Q

Common ligands names - chloride

A

Chlorido

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70
Q

Common ligands names - fluoride

A

Fluorido

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71
Q

Common ligands names - oxalate

A

Oxalato

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72
Q

List the possible d orbitals in octahedral complexes

A

d xy

d yz

d xz

d x2-y2

d z2

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73
Q

Describe the difference in repulsion in d orbital octahedral complexes

A

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

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74
Q

In octahedral complex is in d orbitals where are the first six electrons found

A

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
Q

What does the 🔺E depend on in octahedral complex of d orbitals

A

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
Q

What are ligands that cause a large difference in energy called

A

Ligands that cause a large difference in energy are known as strong field ligand

77
Q

What are ligands that cause a small difference in energy called

A

Ligands that cause a small difference in energy are known as weak field ligands.

78
Q

The spectrochemical series in order from weak field to strong field ligands

A

I- < Br- < Cl- , H20 < NH3 < CN-

79
Q

What happens when a d electron absorbs sufficient energy

A

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
Q

What happens when there’s more than one electron to promote

A

If there is more than one electron to promote, multiple wavelengths can be absorbed

81
Q

What happens when ligands are changed

A

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
Q

What does UV and visible absorption spectroscopy involve

A

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
Q

Approx UV wavelength

A

200nm - 400nm

84
Q

Approx visible wavelength

A

400nm - 700nm

85
Q

What is thought about the unpaired d-electrons or infilled d-orbitals allow

A

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
Q

What are heterogenous catalysis

A

Catalysts in a different state from the reactants

87
Q

What are homogeneous catalysis

A

Catalysts in the same state as the reactants

88
Q

What is thought to play an important part in homogeneous catalysis

A

Variable oxidation states of transition metals

89
Q

Stoichiometry

A

Stoichiometry looks at the ‘amount’ of matter present in a substance. It is the study of the mole relationships involved in chemical reactions.

90
Q

Compare actual yields and theoretical yield

A

Actual yields will always be less than theoretical yield

91
Q

Why will the actual yield always be less than the theoretical yield

A

Mass transfer or mechanical losses

Purification of products

Sage reactions occurring

Equilibrium positions

92
Q

Quantitative reactions

A

They use balance equations and are reactions in which the reactants react completely according to the balanced equation

93
Q

Gravimetric analysis

A

Used to determine the mass of an element or compound in a substance

94
Q

How does gravimetric analysis work

A

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
Q

Gravimetric analysis methods of isolating and purifying

A

Precipitation

Volatilisation

96
Q

Precipitation

A

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
Q

Volatilisation

A

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
Q

Process of heating to a constant mass

A
  • 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
Q

Equilibrium

A

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
Q

What happens as the value of K increases

A

The higher the values of K the more the products side is favoured

101
Q

K = 1 x 10-3

A

Effectively no reaction (mainly reactants in the mixture)

102
Q

K = 1 x 10^3

A

Reaction is effectively complete

103
Q

K between the values of 1 x 10-3 and 1x10^3

A

Reaction is at equilibrium

104
Q

K > 1

A

More products than reactants

105
Q

K < 1

A

More reactants than products

106
Q

K = 1

A

Equal amounts of products and reactants

107
Q

Equilibrium - what are all pure solids and liquids assign the value of

A

1

108
Q

Partial pressure

A

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
Q

Le Chatelier’s Principle

A

“ 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
Q

Concentration affect of K

A

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
Q

Pressure affect of K

A

No overall effect on K

112
Q

Catalyst effect on K

A

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
Q

Temperature affect on K

A

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
Q

Temperature and endothermic reactions

A

Increasing temperature favours endothermic reactions.

115
Q

Temperature and exothermic reactions

A

Decreasing temperature favours exothermic reactions

116
Q

Brønsted-Lowry definition of an acid

A

Acid is a proton donor

117
Q

Brønsted-Lowry definition of a base

A

A base is a proton acceptor

118
Q

What does every acid form

A

Conjugate base formed by the loss of a proton

119
Q

What does every base form

A

Conjugate acid formed by gain of a proton

120
Q

Water dissociation - What happens when water is repeatedly purified

A

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
Q

What term is used to describe water

A

Amphoteric - can act as an acid or a base

122
Q

Ionic product of water value

A

At 298K = 1 x 10^14 mol2l2

123
Q

Ionic product of water symbol

A

Kw

(Subscript w)

124
Q

How does the ionic product of water vary

A

Temperature

As temperature increases Kw increases

125
Q

Strong acid/base definition

A

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
Q

Strong acids

A

Hydrochloric acid (HCl)

Sulphuric acid (H2SO4)

Nitric acid (HNO3)

127
Q

Strong bases

A

Sodium hydroxide (NaOH)

Potassium hydroxide (KOH)

Calcium hydroxide Ca(OH)2

128
Q

Weak acid/base definition

A

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
Q

Weak acids

A

Carboxylic acids

Carbonic acid (H2CO3)

Sulphurous acid (H2SO3)

130
Q

Weak bases

A

Ammonia (NH3)

Ammonium hydroxide (NH4OH)

Amines

131
Q

Equimolar meaning

A

Same number of moles

132
Q

Equimolar solutions of strong and weak acids

A

Have different pH values but the stoichiometry of the reactions are the same

133
Q

Rate, conduction, titration of strong acids/bases compared to weak

A

Rate = faster

Conduction = higher

Titration = same

134
Q

Rate, conduction, titration of weak acids/bases compared to strong

A

Rate = slower

Conduction = lower

Titration = same

135
Q

Why is the rate of strong acid/bases faster than weak

A

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
Q

Why is the conduction of strong acid/bases higher than weak

A

Have more ions that are free to move so conduct better

137
Q

Titration simple explanation

A

As an acid is added to an alkali (or vice versa) it is neutralised.

H+(aq) + OH-(aq) ——> H2O (l)

138
Q

Titration of strong acid /base

A

For the strong acid/base titration/neutralisation will continue until all free ions are used up.

139
Q

Titration of weak acid/base

A

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
Q

What is the result of a titration of the concentrations of the strong and the weak solution are the same

A

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
Q

What determines the pH of the salt produced

A

The strength of the acid and a base used in the neutralisation and the equivalence point of the neutralisation

142
Q

Equivalence point

A

The point at which the reaction has just finished

143
Q

Endpoint

A

The endpoint is where a noticeable change occurs

144
Q

Strong acid strong base salt

A

Neutral salt

145
Q

Strong acid/week base salt

A

Acidic salt

146
Q

Weak acid/strong base salt

A

Basic salt

147
Q

Weak acid/weak base salt

A

Cannot predict without more information

148
Q

What are soaps an example of

A

Sort are examples of weak acids (fatty acids) + strong base (NaOH) so are there for alkaline salts

149
Q

Acid dissociation constant

A

Symbol: Ka (subscript a)

The stronger the acid the higher degree of dissociation so the higher the value for Ka

150
Q

pH of weak acids formula

A

pKa = -log10Ka

151
Q

Acid dissociation formula

A

Ka = [H3O+][A-] / [HA]

(Products over reactants)
Pure solids and liquids given value of 1

152
Q

Buffer solution

A

A buffer solution is a solution in which the pH remained approximately constant, even with additions of small volumes of acid or base.

153
Q

What makes an acidic buffer

A

Weak acid + one of its salt made from a strong base

154
Q

What makes an alkaline buffer

A

Weak base + one of its salts made from a strong acid

155
Q

1st law of thermodynamics

A

Energy is conserved. Energy cannot be created or destroyed, it can only be changed from one form to another

156
Q

Hess’ law

A

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
Q

Enthalpy of formation

A

The enthalpy change when ONE MOLE of a substance is formed from its elements in their standard state

158
Q

What temperature are reactants and products in the standard state

A

298K

159
Q

Define standard state

A

The most stable state at room temperature and pressure

160
Q

Standard pressure and temperature

A

298K
1 atm

161
Q

Midpoint of colour change

A

[In-] = [HIn]

162
Q

When is the colour change distinguishable

A

The colour changes only distinguishable when [HIn] and [In-] differ by a factor of 10

163
Q

Range in which an indicator changes colour

A

pH = pKIn +/- 1

(Subscript In)

164
Q

Who are indicators chosen

A

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
Q

What is entropy (S)

A

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
Q

Second law of thermodynamics

A

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
Q

Degree of disorder and state

A

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
Q

The effect of increasing temperature on disorder

A

Increasing temperature increase is disorder

Increasing temperature increases entropy

(Think of it as going from solid liquid gas)

169
Q

What happens to entropy as a substance melts or boils

A

Rapid increase in entropy as a substance melts. Even more rapid increase in entropy when a substance boils

170
Q

Third law of thermodynamics

A

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
Q

What is the standard entropy of a substance

A

The entropy value for the substance in its standard state

172
Q

Entropy change for a system at equilibrium

A

Will be zero as the amount of disorder remains unchanged

173
Q

Gibbs free energy

A

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
Q

Favourable conditions for a reaction

A

🔺H should be negative
🔺S should be positive
🔺G should be negative to show a release in energy

175
Q

Free energy (G) calculation

A

🔺G* = 🔺H* - T🔺S*

176
Q

🔺G negative

A

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
Q

Applying the concept of free energy understand of conditions

A

🔺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
Q

When will a reaction process

A

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
Q

Applying the concept of free energy under non-standard conditions

A

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
Q

What is the state that controls the rate of reaction called

A

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
Q

How can order of reaction be determined

A

The order of a reaction can only be determined experimentally as reactions may go through a series of steps called the reaction mechanism

182
Q

How does rate (k) vary

A

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
Q

Common ligands name - carbon monoxide

A

Carbonyl

AH Chem (2 decks)

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