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topic 15 Flashcards

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1
Q

where are the d block elements on the periodic table

A

d block elements are the in the middle of the periodic table

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2
Q

what is a transition metal

A

a transition metal is a d block element that can form at least one stable ion with partially filled incomplete d-subshell

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3
Q

recall the transition metals

A

titanium
vanadium
chromium
manganese
iron
cobalt
nickel
copper

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4
Q

how many electrons can a d sub-shell hold

A

10

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5
Q

what is an atomic orbital

A

a space in which the chance of an electron occurring is at its highest level

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6
Q

why are zinc and scandium not transition elements

A

this is because they dont form a stable ion with a partially filled d-subshell

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7
Q

recall the box notation for the electronic configuration of titanium

A

[Ar] ->

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8
Q

recall the box notation for the electronic configuration of vanadium

A

[Ar]

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9
Q

recall the box notation for the electronic configuration of chromium

A

[Ar]

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10
Q

recall the box notation for the electronic configuration of manganese

A

[Ar]

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11
Q

recall the box notation for the electronic configuration of iron

A

[Ar]

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12
Q

recall the box notation for the electronic configuration of cobalt

A

[Ar]

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13
Q

recall the box notation for the electronic configuration of nickel

A

[Ar]

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14
Q

recall the box notation for the electronic configuration of copper

A

[Ar]

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15
Q

how do the subshells fill up and why
Which shell fills up first

A

the subshells fill up singly before pairing up due to the electrons repelling each other
4s fills up first

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16
Q

why does one of the 4s electrons in chromium go to the 3d orbital

A

because it has the opportunity to have a half full subshell which is stable

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17
Q

why does the last electron in manganese go to the 4s orbital

A

its lower in energy

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18
Q

why does the electron from the 4s orbital in copper go to the 3d orbital

A

forms a full 3d subshell which is more stable than the electron being in the 4s orbital

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19
Q

why does the copper and chromium electrons move from the 4s to the 3d orbital

A

to create a more stable half full or full 3d subshell

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20
Q

why is scandium not a transition element

A
  • scandium only forms one stable ion Sc3+
  • Sc3+ it has an empty d-subshell → since its not partially filled (when its an ion) its not a transition element
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21
Q

recall the box notation for scandium and Sc3+

A
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22
Q

why is zinc not a transition element

A
  • zinc only forms one stable ion → Zn2+
  • Zn2+ has a full d-subshell
    • since its not partially filled its not a transition element
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23
Q

recall the box notation for the electronic configuration of zinc and Zn2+

A
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24
Q

how do transition metals lose electrons

A

always lose e- from the 4s orbital first

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25
Q

recall the properties of transition metals

A

variable oxidation states to form coloured ions in solution
are good catalysts
can form complex ions
have high mtp and bpts

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26
Q

why do transition metals have variable oxidation states

A

because their d-orbitals are never fully filled so they can accommodate more electrons

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27
Q

why are electrons lost and gained from transition metals using a similar amount of energy

A

because the electrons sit in the 4s and 3d energy levels which are very close

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28
Q

why do transition metals have various different colours

A

when they form ions (lose e-) they have various different colours

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29
Q

recall the different ions that vanadium can form

A

V2+
V3+
VO 2+
VO2 +

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30
Q

recall the different ions that chromium can form

A

Cr3+
Cr2O7 2-

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31
Q

recall the different ions that manganese can form

A

Mn2+
MnO4 2-
MnO4 -

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32
Q

recall the different ions that iron can form

A

Fe2+
Fe3+

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33
Q

recall the ions that cobalt can form

A

Co2+

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34
Q

recall the ions that nickel can form

A

Ni2+

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35
Q

recall the ions that copper can form

A

Cu2+

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36
Q

recall the ions that titanium can form

A

Ti2+
Ti3+

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37
Q

what are the colours of vanadiums ions when dissolved in water

A

V2+ → violet

V3+→ green

VO 2+ → blue

VO2 + → yellow

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38
Q

what are the colours of chromium ions when dissolved in water and explain the colour for the Cr3+ ion

A

Cr3+ → green/violet

  • its violet when its surrounded by 6H2O ligands
  • they are normally substituted so usually look green

Cr2O7 2- → orange

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39
Q

what are the colours of manganese’s ions when dissolved in water

A

Mn2+ → pale pink

MnO4 2- → green

MnO4- → purple

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40
Q

what are the colours of irons ions when dissolved in water

A

Fe2+ → pale green

Fe3+ → yellow

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41
Q

what are the colours of cobalts ions when dissolved in water

A

Co2+ → pink

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42
Q

what are the colours of nickels ions when dissolved in water

A

Ni2+ → green

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43
Q

what are the colours of coppers ions when dissolved in water

A

Cu2+ → blue

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44
Q

what are the colours of titaniums ions when dissolved in water

A

Ti2+ → violet

Ti3+ → blue

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45
Q

what is a complex ion

A

a complex ion is where a central transition metal ion is surrounded by ligands bonded by dative covalent bonds

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46
Q

what are ligands

A

ligands have at least 1 lone pair of electrons where they are used to form dative covalent bonds with the metal
ligands are lewis bases and nucleophiles
the lone pair in the ligand is used to fill the d orbital of the transition metal ion

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47
Q

draw the general structure of a complex ion

A
  • square brackets show the full complex and the overall charge of the complex sits outside of the brackets
  • complex ions can come in different shapes as well
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48
Q

what can ligands be

A

they can be monodentate, bidentate or polydentate

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49
Q

what are monodentate ligands and give examples

A
  • ligands that can only form a single coordinate bond
    • example H2O, NH3, CL-, OH-, Br-, I-
      only one atom in the molecule has the lone pair of electrons
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50
Q

what are bidentate ligands

A

ligands that have 2 atoms in the molecule which have a lone pair of electrons are called bidentate ligands and can therefore form 2 coordinate bonds

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51
Q

give two examples of bidentate ligands and draw their structure

A
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52
Q

what is a multidentate ligand

A

contain more than 2 atoms that donate pairs of electrons to form coordinate bonds

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53
Q

give an example of a multidentate ligand

A

EDTA+→ can form 6 coordinate bonds with the central metal ion
ethylenediaminetetracetic acid

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54
Q

what does the shape of a complex ion depend on

A

the shape is dependent on the size of the ligand and the coordination number

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55
Q

what is the coordination number

A

the number of coordinate bonds in a complex (not the number of ligands)

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56
Q

using the example of EDTA+ explain what a coordination number is

A

EDTA+ can form 6 coordinate bonds but theres only one ligand → so the coordination number of this complex is 6 not 1

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57
Q

how many small ligands can you fit around a central metal ion

A
  • some ligands are small so you can fit 6 of them around a central metal ion
    • e.g water, ammonia, hydroxide ions
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58
Q

how many large ligands can you usually fit around a central metal ion

A

some ligands are larger so you can only fit 4 of them around the central metal ion

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59
Q

how many bidentate ligands can you fit around a central metal ion

A

ethanedioate and ethane-1,2-diamine are larger → normally you have 3 of these around a central metal ion

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60
Q

which complex ions form octahedral shapes and give the bond angle

A

complexes with a coordination number of 6 form octahedral shapes
all bond angles in an octahedral complex are 90 degrees

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61
Q

draw and name 2 examples of complex ions with an octahedral shape using the example of covalt

A
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62
Q

which complexes form a tetrahedral or square planar shape

A

complexes with a coordination number of 4 form tetrahedral and square planar

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63
Q

draw and name an example of a tetrahedral complex ion and the bond angle

A
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64
Q

draw the structure of cis-platin and give the bond angle

A

bond angles in a square planar complex are always 90 degrees
trans-platin-> CL is opposite
used in cancer treatment

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65
Q

what are the charges of complexes

A

complexes always have an overall charge which is the same as its total oxidation state

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66
Q

how do you calculate the total oxidation state of the metal in the complex

A

total oxidation state of the complex - total oxidation state of the ligands

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67
Q

give an example of a total oxidation state calculation using [CuCl4]2+

A
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68
Q

what is haem an example of and what is it used for

A
  • haem is a multidentate ligand that is found in haemoglobin
  • it is a protein used to transport oxygen around the body in blood
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69
Q

what is the structure of haemoglobin

A
  • the structure is octahedral
  • one of the coordinate bonds come from a large protein called globin
  • the final coordinate bond comes from either an oxygen or water molecule
  • 4 of the nitrogens which are circled comes from a multidentate ligand called haem
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70
Q

how does haemoglobin work

A
  • oxygen substitutes the water ligand (happens in the lungs) → where oxygen conc. is high to form oxyhaemoglobin which is transported around the body
    • oxygen binds on top
  • taken to muscles to allow respiration to occur
  • oxyhaemoglobin gives up oxygen to a place where its needed
  • water takes the place and haemoglobin returns back to the lungs → process starts again
    • we breathe out water vapour as well as is one of the products of respiration
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71
Q

what is carbon monoxide

A
  • carbon monoxide → poisonous gas
    • causes headaches, unconsciousness and even death
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72
Q

what happens is carbon monoxide if inhaled

A

if carbon monoxide is inhaled → water ligand is replaced with a carbon monoxide ligand
- carbon monoxide bonds strongly → so its not readily replaced by oxygen or water
- this means oxygen cant be transported → carbon monoxide transported instead
- leads to oxygen starvation which is why CO is poisonous
- unconsciousness→ not enough oxygen going to the brain

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73
Q

draw the structure of carbon monoxide bonded to haemoglobin

A
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74
Q

what can complex ions show

A
  • complex ions show optical isomerism
  • complexes are optical isomers when they are non superimposable images
  • can also show cis-trans isomerism
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75
Q

which type of complex shows optical isomerism- draw an example

A

octahedral complexes (which have 6 coordinate bonds) with 3 bidentate ligands show optical isomers such as the one above

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76
Q

what kind of complexes can show cis-trans isomerism

A

octahedral complexes with 4 ligands of the same type and 2 ligands of a different type display cis-trans isomerism
square planar complexes with 2 ligands of the same type and 2 ligands of a different type display cis-trans isomerism

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77
Q

give an example of an octahedral complex which shows cis-trans isomerism

A
  • if the 2 different ligands are opposite each other → trans isomer
  • if the 2 different ligands are adjacent to each other → cis isomer
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78
Q

give an example of a square planar complex which shows cis-trans isomerism

A
  • if different ligands are opposite each other → trans isomer
  • if different groups are adjacent to each other → cis isomer
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79
Q

why are transition metals colourful

A

d-orbital splitting

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80
Q

how does d orbital splitting occur

A

the d-subshell is split into 2 when ligands bond with the central metal ion
when we attach ligands → the 5 orbitals in a d-subshell start to split

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81
Q

how is an energy gap created

A
  • when we attach ligands → the 5 orbitals in a d-subshell start to split
  • energy gap is created as some orbitals gain energy
    • ΔE → change in energy
82
Q

draw an example of ground state and what is it

A

the lowest energy level

83
Q

draw an example of excited state and explain it

A

when electrons absorb light energy some move from the lowest energy level (ground state) to higher energy level orbitals (excited state)

84
Q

for electrons to move to excited state/ higher energy level orbitals what must be the case

A

in order for this to happen, the energy from the light must equal the energy gap

85
Q

what is the size of the energy gap/energy change dependent on

A
  • the central metal ion and its oxidation state
  • the type of ligand
  • shape of ligand
  • the coordination number and therefore shape of the complex
86
Q

what frequency of light is absorbed by the complex

A
  • some frequencies of visible light are absorbed by transition metal complexes
  • frequencies absorbed depends on the size of ΔE
  • the larger the energy gap, the higher the frequency of light absorbed
87
Q

what is an energy gap

A

the energy required to take an electron from the ground state to an excited state

88
Q

which colours of visible light have the highest and lowest frequency

A
  • from red to purple → frequency increases
    • red→ lowest frequency
    • violet → highest frequency
89
Q

what happens to the frequencies of light that arent absorbed

A

any frequencies which arent absorbed are reflected or transmitted
e.g if a transition metal ion absorbs at the green frequency of light then all of the other colours around it are reflected or transmitted out of the complex

90
Q

what do the transmitted or reflected frequencies create

A

the combination of these frequencies create a complimentary colour that we observe
this is different to heating any other metal and observing colour (for other metals the colour is due to when the electron deexcites)

91
Q

what frequency of light do we observe from a complex

A

we observe the colour that is complimentary to the frequency of light that is absorbed by the complex

92
Q

how do we determine which frequency is absorbed

A
  • the colour wheel allows us to predict the colour of light absorbed
  • the colour directly opposite the colour is observed is the one thats absorbed
    • e.g green observed, magenta absorbed
93
Q

draw the colour wheel

A
94
Q

why may some complexes be observed as colourless or white

A
  • for the complexes that have a full or empty 3d subshell no e- can move to the higher energy level
    • this means that we see these complexes as colourless or white e.g Zn, Sc
95
Q

what is white light made up of

A

made of all colours

96
Q

what happens if you mix the complementary colour and the absorbed colour

A

you get white light

97
Q

what do redox potentials tell you

A

redox potentials tell us how easily an ion is reduced → the same as the electrode potentials

98
Q

what ions are more likely to be reduced

A

the least stable ions have the largest redox potential → more likely to be reduced

99
Q

why may there be a difference in redox potential to the standard values seen in the data booklet

A

here may be a difference in redox potential to the standard values seen in the data booklet →dependent on the environment the ions are in

100
Q

what happens when a transition metal changes oxidation state

A

redox reaction occurs

101
Q

give the half equation for the reduction of V2+ to V and the colour + oxidation state

A

Os- +2
violet

102
Q

give the half equation for the reduction of V3+ to V2+ and the colour + oxidation state

A

Os- +3
green

103
Q

give the half equation for the reduction of VO 2+ to V3+ and the colour + oxidation state

A

Os- +4
blue

104
Q

give the half equation for the reduction of VO2 + to
VO 2+ and the colour + oxidation state

A

Os- +5
yellow

105
Q

when are redox reactions feasible

A

only feasible if standard electrode potential is positive

106
Q

recall the colour changes of the reduction of VO2 + to V2+

A
107
Q

why are there no more colour changes after V2+

A

no more colour change after V2+ as the standard electrode potential is negative → no longer feasible

108
Q

what are the variable oxidation states of chromium

A

+2, +3, +6

109
Q

give the colour, oxidation state and any addition information on Cr2O7 2-

A

+6
orange
good oxidising agent

110
Q

give the colour, oxidation state and any addition information on CrO4 2-

A

+6
yellow
good oxidisng agents

111
Q

give the colour, oxidation state and any addition information on Cr3+

A

+3
green
most stable ion when surrounded by 6 water ligands a violet solution
however Cl- impurities replace the water ligands to make it look green

112
Q

give the colour, oxidation state and any addition information on Cr2+

A

+2
blue

113
Q

give the colour change and reduction equation for Cr2O7 2- to Cr3+

A
  • Cr2O7 2- can be reduced using zinc as a catalyst to 2Cr3+
    • colour change from orange to green
114
Q

give the colour change and reduction equation for Cr3+ to Cr2+

A
  • zinc can be used to reduce Cr3+ ions to Cr2+ ions
    • however Cr2+ → unstable
      • readily oxidised back to Cr3+ from oxygen in the air
        colour change from green to blue
115
Q

how can Cr3+ ions be oxidised to CrO4 2- ions- give the equation

A
  • Cr3+ ions are oxidised using hydrogen peroxide in alkaline solution
  • yellow chromate (VI) produced
116
Q

Give the equation for when you add acid to CrO4 -

A

adding acid to the yellow chromate (VI) ion solution creates orange dichromate (VI) solution

117
Q

what does amphoteric mean with the example of chromium hydroxides

A

chromium hydroxides can act as an acid or base → means they are amphoteric

118
Q

how can you form insoluble chromium hydroxide

A

can hydrolyse metal aqua ions to form insoluble chromium hydroxide by adding a base (OH- or NH3)

119
Q

give the equations for forming insoluble chromium hydroxide

A
  • they form a solid complex as theres no longer a charge
  • added 3 negative OH- ligands which balances out the 3+ of the Cr(H2O)6 → neutral solid complex→ precipitate
  • ammonia takes 1 proton each from the 3 water ligands which forms ammonium ions
  • green grey precipitate forms
120
Q

give the formula for chromium hydroxide

A

Cr(H2O)3(OH)3

121
Q

what happens when you add a base to chromium hydroxide + give the equation

A
  • when you add a base to it → acts as an acid and donates H+ ions to react with the OH- and it dissolves
  • this is because it will have a charge when it donates H+ ions
122
Q

what happens when you add an acid to chromium hydroxides- give the equation

A

when we add an acid it acts as a base by accepting H+ ions and it dissolves

123
Q

what happens if you add excess ammonia to chromium hydroxides and give the equation

A

→ ligand exchange reaction
- purple Cr(NH3)6 3+ solution is formed
- green-grey to purple colour change
- ligands that were attached are now separated

124
Q

how do you produce chromium II ethanoate

A
125
Q

how can a colour change of complexes occur

A

a colour change can exist when ligands in a complex exchange/ substitute
change in coordination number and shape of complex

126
Q

give an example of how different ligands can form different strength bonds to the metal ion using CN

A
  • CN- ions can form stronger bonds than the H2O molecules
  • this means that the reaction isnt easily reversed
  • the new complex formed is more stable

this is added to salt → STOPS SALT FROM STICKING TOGETHER

127
Q

what can multidentate ligands form- give an example of this

A

multidentate ligands form complexes that are more stable than monodentate ligand
in e.g
- 6 ligands replaced by 3
- stable → hard to reverse

128
Q

what is the link between entropy and complexes

A
  • entropy increasing forms a more stable complex
  • in a ligand exchange reaction bonds are broken in the original complex
  • new bonds are formed to make the new complex
  • often, energy needed to break the bonds is similar as the energy released when new ones are formed
    • the enthalpy change is small
129
Q

what is the chelate effect

A
  • when we substitute monodentate ligands with bidentate and multidentate ligands → creates a solution with more particles in it
    • this means theres as increase in entropy
    • this means that the reaction is more likely to happen
    • difficult to reverse these reactions as this would mean that theres a decrease in entropy (less likely to happen)
130
Q

give an example of the chelate effect using EDTA+

A
131
Q

what does the colour of the complex ion depend on

A

depends on the size of ΔE which is affected by a change of oxidation state, coordination number and change of ligand

132
Q

give an example of where ligands have an effect on the energy gap- give the equation, colour changes and the shape using Co

A

e.g → ligand substitution where the coordination number is the same and so is the shape

133
Q

give an example of ligand substitution where coordination number changes and so does the shape using Cu

A

normally happens when a smaller ligand is substituted by a larger ligand

134
Q

what is the formula for metal ions dissolved in water

A

[M(H2O)6] n+

135
Q

give the colour and formula of Cu2+ ions in aqueous solution

A

[Cu(H2O)6]2+
blue

136
Q

give the colour and formula of Fe2+ ions in aqueous solution

A

[Fe(H2O)6]2+
pale green

137
Q

give the colour and formula of Fe3+ ions in aqueous solution

A

[Fe(H2O)6]3+
yellow

138
Q

give the colour and formula of Co2+ ions in aqueous solution

A

[Co(H2O)6]2+
pale pink

139
Q

give the colour of the precipitate formed and the formula when you add some OH- or NH3 to Cu2+

A

Cu(OH)2(H2O)4
pale blue

140
Q

give the colour of the precipitate formed and the formula when you add some OH- or NH3 to Fe2+

A

Fe(OH)2(H2O)4
dirty green

141
Q

give the colour of the precipitate formed and the formula when you add some OH- or NH3 to Fe3+

A

Fe(OH)3(H2O)3
orange

142
Q

give the colour of the precipitate formed and the formula when you add some OH- or NH3 to Co2+

A

Co(OH)2(H2O)4
blue
turns brown after a while

143
Q

what happens when you add excess OH- to Cu(OH)2(H2O)4

A

insoluble in excess NaOH
no change

144
Q

what happens when you add excess OH- to Fe(OH)2(H2O)4

A

insoluble in excess NaOH
no change

145
Q

what happens when you add excess OH- to Fe(OH)3(H2O)3

A

insoluble in excess NaOH
no change

146
Q

what happens when you add excess OH- to Co(OH)2(H2O)4

A

insoluble in excess NaOH
no change

147
Q

what happens when you add excess NH3 to Cu(OH)2(H2O)4

A

[Cu(NH3)4(H2O)2]2+ forms
dark blue solution
part ligand substitution

148
Q

what happens when you add excess NH3 to Fe(OH)2(H2O)4

A

insoluble in excess NH3
no change

149
Q

what happens when you add excess NH3 to Fe(OH)3(H2O)3

A

insoluble in excess NH3
no change

150
Q

what happens when you add excess NH3 to Co(OH)2(H2O)4

A

Co(NH3)6 2+
brown-yellow solution
turns brown after a while

151
Q

recall this table

A
152
Q

what is a heterogeneous catalyst and how does it work

A
  • heterogeneous → catalyst in different phase from reactants
    • reaction occurs on the surface of a catalyst
    • increasing the surface area of the heterogenous catalyst will increase the rate of reaction
      • more particles can react with the catalyst at the same time
153
Q

what is a homogeneous catalyst and how does it work

A
  • form intermediate species by reactants combining with the catalyst to form products
  • the catalyst is reformed again
154
Q

why are transition meals good catalysts

A

as transition metals have variable oxidation states they are good catalysts → by receiving and losing some e- in the d-orbitals to speed up reactions

155
Q

what is the contact process

A
  • the contact process uses vanadium (V) to make sulfuric acid
  • V2O5 used as a catalyst → heterogenous catalyst
    • catalyse SO2 → SO3
156
Q

recall the steps and equations for the contact process

A
157
Q

how can heterogeneous catalysts be poisoned

A
  • heterogeneous catalysts can be poisoned be impurities
  • impurities can bind to surface of a catalyst and block the active site for reactants to absorb
  • when an impurity blocks a site→ called poisoning
158
Q

what is the effect of catalysts being poisoned and draw an image to show it

A

catalytic poisoning reduced surface area of catalyst for the reactants to add to

159
Q

what is an example of poisoning from the haber process

A
  • hydrogen is made from methane
  • methane contains sulphur impurities
  • any sulphur that is not removed will absorb to the surface forming iron sulphide
    • catalyst less efficient
160
Q

what is the effect of a poisoned catalyst

A
  • less product is made
  • catalyst needs to be replaced/cleaned more often → time consuming
  • increased cost of the chemical process
    • not lowering activation energy
161
Q

how do heterogeneous catalysts work with reference to adsorption and desorption

A
  • substances can absorb to the surface of solid heterogeneous catalyst
  • reactions occur on solid heterogeneous catalysts
    • they bond with the surface of the catalyst → adsorption
  • the bonds in the reactants weaken and break → form radicals
  • the radicals react with each other to make new substances
  • the new molecules are then released from the surface of the catalyst in a process called desorption
162
Q

what is desorption

A

the new molecules are then released from the surface of the catalyst in a process called desorption

163
Q

what is adsorption

A

substances bond with the surface of the catalyst → adsorption

164
Q

draw an image of adsorption and desorption

A
165
Q

why use catalysts

A
  • lower temp needed for reaction to proceed
    • less money spent and less CO2 produced
  • speed up reaction → provide alternative pathway for the reaction to proceed

environmental benefits using a catalyst

  • lower temp + pressure required
    • reduced energy and CO2 produced
    • less waste → increase atom economy. instead of e.g a 5 step process it becomes a 2 step process
166
Q

what are catalytic converters and give their equation

A
  • in cars
  • reduce levels of pollution
  • made from rhodium, platinum and palladium alloy
  • mesh → gases pass through
167
Q

how can vehicle catalysts be poisoned

A
  • vehicle catalysts can be poisoned too
  • e.g lead poisons the platinum catalyst in a catalytic converter in a car
  • lead was found in petrol but is now no longer used widely today → hence unleaded
  • the poison absorbs to the surface of the catalyst better than the reactant can
    takes up space
168
Q

draw the energy profile of a reaction with a homogeneous catalyst

A

homogeneous energy profiles have 2 activation energies
- green line → activation energy with the catalyst
- lowers activation energy
- two activation energies → this is because intermediates are formed at the point shown in the diagram below
- then a bit more energy is required to produce the final product
- heterogeneous catalysts forms intermediate species by reactants combining with the catalyst which react to form products
- catalyst is reformed again→ never used up
- lowers activation energy

169
Q

how can iodide ions be oxidised

A

oxidation of iodide ions using peroxodisulfate (S2O8 2-)

  • reaction uncatalysed is very slow
  • trying to react negatively charged ions together which repel
    • results in high activation energy
170
Q

recall the process of oxidising iodide ions using peroxodisulphate

A
171
Q

what is autocatolysis

A
  • is another form of heterogeneous catalysis where the product catalyses the reaction
    • catalyses itself
172
Q

give an example of autocatalysis using Mn2+

A

Mn2+ is the catalyst in a reaction between C2O4 2- and MnO4-

  • Mn2+ is a product and catalyst
    • as the reaction proceeds the amount of product increases and so does rate of reaction
  • the reaction uncatalysed is slow as youre trying to react two negative ions which will repel
173
Q

recall the process of Mn2+ catalysing the reaction between C2O4 2- and MnO4-

A
174
Q

How do you work out the colour changes going from one complex to forming a new one

A

Look at the oxidation state of the transition metal in the complex
Refer to the colour of ion in aqueous solution e.g if the original metal complex contained Fe3+ and the oxidation state decreased to Fe2+ in the new complex the colour change would be from the colour of Fe3+ in aqueous solution to the colour of Fe2+ in aqueous solution

175
Q

what is a complex ion

A

an ion in which a central metal atom (transition element) is surrounded by a group of ions or molecules (ligands)

176
Q

why can transition metals form complex ions

A

transition metals are able to form complex ions due to their small ionic radius
this gives rise to a stronger electrostatic field of attraction
this means that ligands are able to bond to them as they are attracted to the positive charge
this is also why transition metals have high mtp and bpts and are harder than other metals

177
Q

how do you name ligands/ complexes

A

number of ligands e.g di, tri, tetra, penta, hexa

add an -o to the end of ligand name
e.g for chlorine it would be chloro-
for water is would be aqua
for ammonia - ammine

positive complex- ending in transition element name and then oxidation state in roman numerals in brackets at the end
negative iron complex- end in ferrous

178
Q

which is isomer of platin is more effective and why

A

cis-platin is more effective as it prevents cell division
it forms a bond between the 2 DNA strands which disrupts replication
it binds to guanine

trans-platin is toxic

179
Q

why would you not make platin on its own and give it to a patient

A

racemic mixture of cis and trans platin
you dont know how much cis platin there is in the mixture so you dont know whether it would be effective

180
Q

what may cause colour changes in transition metals and why

A

any of the following can cause the colour of complex ion to change
- oxidation number of metal ions -> redox
- ligand gains or loses H+ -> acid-base
- ligands are exchanged -> ligand exchange
- number of ligands change -> coordination number change

this is because these factors change the size of the energy gap

181
Q

How does the d orbital split

A

2 in the higher energy level
3 in the lower energy level

182
Q

give an example of a redox reaction which causes a colour change in the complex ion

A

[Fe(H2O)6]2+ -> [Fe(H2O)6]3+
pale green yellow/brown

in air

183
Q

give an example of an acid base reaction which causes a colour change in the complex ion

A

[Cu(H2O)6]2+ + 2OH- -> [Cu(H2O)4(OH)2] + 2H2O
pale blue solution blue precipitate

it is acid base because 2 OH- ions have removed two of the water ligands and converted them into water
the two water molecules that have lost hydrogen ions are now hydroxide ligands

184
Q

give an example of a ligand exchange reaction that causes a change in colour of the complex ion

A

[Cu(H2O)6]2+ + 2NH3 -> [Cu(H2O)4(OH)2] + 2NH4+
pale blue solution blue ppt
[Cu(H2O)4(OH)2] + 4NH3 -> [Cu(NH3)4(H2O)2]2+
DEEP blue ppt

185
Q

give an example of a reaction where a change in coordination number causes a change in colour of complex ion

A

also done ligand exchange aswell as change in coordination number

186
Q

why do transition metal complexes form coloured solutions

A

when ligands attach -> causes d orbital splitting
2 excited state, 3 round state
produces an energy gap
light energy is absorbed by the electron so it excites to excited state
the rest of the frequencies of light that arent absorbed are reflected and combine to produce a complimentary colour on the colour wheel to the one absorbed

187
Q

how can [Co(NH3)6]2+ be formed? give the shapes, equation and colour changes

A

pink to straw
both complexes octahedral

188
Q

how can [CoCL4]2 be formed? give the shapes, equation and colour changes

A

pink to blue
octahedral to tetrahedral

189
Q

how can [Fe(CL)4]- be formed? give the shapes, equation and colour changes

A

stays yellow (no colour change)
octahedral to tetrahederal

190
Q

Reactions of Cu2+ with OH-, NH3 and excess NaOH and excess NH3 + colour change

A
191
Q

Reactions of Fe2+ with OH-, NH3 and excess NaOH and excess NH3 + colour change

A
192
Q

Reactions of Fe3+ with OH-, NH3 and excess NaOH and excess NH3 + colour change

A
193
Q

Reactions of Co2+ with OH-, NH3 and excess NaOH and excess NH3 + colour change

A
194
Q

what does a negative Ecell value mean

A

indicates equilibrium lies to the LHS (oxidation)

195
Q

what does it mean if Ecell is >0.6

A

reaction will always happen/ always be feasible

196
Q

Copper oxide (black solid) + sulfuric acid

A

copper sulphate

197
Q

Copper sulphate + KI

A

copper (I) iodide

198
Q

Copper (I) iodide + NH3

A

Cu(NH3)2 + (colourless)

199
Q

Copper (I) iodide + H2SO4

A

copper (pink solid) and copper sulphate (blue)

200
Q

Cu(NH3)2 + vigorous shaking

A

Cu(NH3)4(H2O)2 (dark blue)

201
Q

Cu(OH)2(H2O)4 + heat

A

copper oxide (black solid)

[OBSELETE] S - Chem (19 decks)

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