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second year a level chemistry > transition metaks > Flashcards

transition metaks Flashcards

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1
Q

What are transition metals?

A

= these have incomplete d-subshells
= d subshells can hold up to 10 electrons, 5 orbitals

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2
Q

What are the main characteristics of transition metals?

A

= form coloured compounds
= complex ions
= variable oxidation states
= hetergenous and homogenous catalysts

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3
Q

why is zinc not a trannsition metal?

A

= has a complete d-subshell

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4
Q

What is a complex?

A

= metal ion surrounded by ligands
examples: [Ag(Nh3)2]+
=

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5
Q

What is a ligand?

A

= these are atoms, compounds and molecules with a lone pair of electron that can forma dative covalent bond wth a central metal ion
= donates lone pair of electron

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6
Q

What is the coordination number?

A

= no of dative covalent bonds formed to a central metal ion

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7
Q

What are examples of monodentate ligabds?

A

= Nh3
= H2O
= :Cl

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8
Q

What are examples of bidentate ligands?

A

= ethandioate
= ethane-1-2-diame
=

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9
Q

what are multidetate ligabds?

A

= EDTA4-

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10
Q

What are subsitution reactions?

A

= these can happen with ligands of the same size, different size and different strength

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11
Q

What is the normal reaction of colbalt with ammonia?

A

[CO(H2O)6]2+ + 6Nh3 => [Co(Nh3)6]2+ + 6H2O
= the charge remains unchanged- with ligands of the same size, and the coordination number is the same (number of dative covalent bonds)
= therefore this would still be an octahedral shape

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12
Q

What are examples of octahedral shape if needed to be drawn?

A

= copper or colbalt with 6 water or 6 ammonias

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13
Q

What is the partial subsitution of copper and ammonia?

A

[Cu(H2O)6]2+ + 4Nh3 => [Cu(Nh3)4(H2o)2]2+
= 4H2O
= this is only partial
= the coordiation number however remains the same and the number of dative covalent bonds so the charge remains the same

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14
Q

What happens with the reaction with chloride ions?

A

= these are a different shaped ligand- and only react with 4Cl-, therefore the shape changes as the coordination nuber changes and the no of datibe covalent bonds
= with copper the charge goes from +2 to 2- and with colbalt
= with iron it goes from 3+ to -
= replaces the water to form 4 chlorine and them produces 6 water

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15
Q

What is the colour of [CuCl4]2- ?

A

= yellow/green solution
= tetrahedral shape

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16
Q

What is the colour of [CoCl4]-

A

= this is a blue solution
= tetrahedral shape

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17
Q

What example do we use for tetrahedral shapes?

A

= [cucl4]2-
= this is a tetrahedral
109.5 degrees
=

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18
Q

What example do we use for square planar?

A

= cis platin
90 degrees

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19
Q

What example do we use for a linear shape?

A

= tollens reagant
= 180 degrees

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20
Q

What examples can we use for cis trans isomerism?

A

[cr(H2o)4cl2]+

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21
Q

How do colour changes arise?

A

= changes in oxidation state
= coordination number
= ligands

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22
Q

How does colour formed?

A

= electron transitions from the ground state to the excited state, creates a gap in energy and a split in the d-orbital into 2 orbitals, sub-shells, this creates an energy gap
= a portion of visibke light is absorbed and this causes this split, light not absorbed and transmitted displays the colour

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23
Q

What is the first equation to find the difference in energy between split orbitals?

A

= plancks constant
x
= frequency of light absorbed

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24
Q

What is the second wquation to find the difference in energy split between orbitals?

A

= plancks consyant x speed of light/ wavelength of light

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25
Q

Why are so compounds colourless and are white?

A

= empty
= full subshell
= so cannot split the d-orbital- so no transmission of electrons from ground state to excied state
= there is not an energy transfer equal to that of visible light

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26
Q

What do compounds with high oxidation states tend to be?

A

= oxidising agents

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27
Q

What do compounds with low oxidation states tend to be?

A

reducing agents

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28
Q

What oxidation state does Vo2+ have?

A

= +5
= yellow solution

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29
Q

What oxidation state and colour does VO 2+ have?

A

= +4
= blue solution

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30
Q

What oxidation state does v3+ have?

A

= +3
= green solution

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31
Q

What oxidation state does v2+ have?

A

= violet colour
= +2

32
Q

How can we reduce vanadium?

A

= using zinc in acidic solution
= the equations have 2 moles of the vanadoum compound
= 4H+ on LHS
Zn2+ on rhs
= and 2 water
= we do not have water and 4H+ on the last one

33
Q

What do catalysts do?

A

= speed up rate of reaction without being used up- reducing the activation energy
= transition metals can act as heterogenous or homogenous catalysts

34
Q

What is the simple concept for heterogenous catalysts?

A

= different phase from the reactants

35
Q

What are the general concept for homogenous catalysts?

A

= samephase as the reactants

36
Q

what are heterogenous catalysts?

A

= = usually solids, whilst the reactahts are gaseous in a solution, reaction occurs at surface of catalyst
= different phase from the reactants

37
Q

How do these catalysts work? heterogenous

A

= reactants form bonds with atoms at active sites on the surface of the catalyst
= as a result, bonds in the reactants are weakened and break
= new bonds form between the reactants held close on the catalytic surface
= weakens the bonds between product and catalyst and product leaves
= ADSORPTION

38
Q

What are the strengths of adsorption?

A

= determine effectibvness
= some metals are too strong adsorption, producys cannot be released
= somemetals are too werak adosorption, and do not adsorb in high enough concetration
= ni and platinium have the right ebogh catalyst

39
Q

What catalust is used in the comtact process?

A

= = V2O5 is the catalyst- remember these are never used up
= 2SO2 + O2 => 2SO3

40
Q

What is step 1 od rhe contact process?

A

[= = SO2 + V2O5 => SO3 + V2O4

41
Q

What is step 2 of the contact process?

A

= = 2V2O4 + O2 => 2V2O5

42
Q

How are catalysts posioned?

A

= = catalysts can be posioned by impurities and reduces efficiency and may need to be replaced
= less product is made
= increaes cost of chemical proceses
=

43
Q

What are homogenous catalysts?

A

= when catalysts and reactants are the same state, the reaction uses an in intermediate that reacts to form producy and regenerates the catalyst

44
Q

What will the interediate tends to have?

A

= different oxidation states to the oriignal transition metal

45
Q

Why do transition metals make good homogemous catalysts?

A

= form various oxidation states, able to donate and recieve electrons

46
Q

What ar are the reactions between I- and S2O82- ?

A

S2O8 2- + 2I- => 2So4 2- + I2

47
Q

What are the 3 reactions that need to be leart?

A

S2O8 + 2e- => 2So4 2-
Fe3+ + e- => Fe2+
I2 + 2e- => 2I-

48
Q

Why is the uncatalustsed reaction vert slow?

A

= reaction needs a collision between 2 negative ions repulsiomeans there is a high activation energy

49
Q

What is the catalysed alternative route?

A

= S2O8 + 2Fe2+ -> 2So42- + 2Fe3+

= 2I- + 2Fe3+ => 2Fe2+ + I2

50
Q

What is an autocatalytic reaction?

A

= = where one of the products, of the reaction can catalyse the reaction
= the catalyst is not used up and is reformed

51
Q

What makes a reaction have a high activation energy?

A

= = if there are 2 negative ions repel eachother and this causes a high activation energy

52
Q

How do autocatalysts work?

A

= product acts as a catalyst, so after slow start the reaction begins to speed up, as they provide an alternate route with lower activation energy
= the reaction slows down as the catalyst product drops

53
Q

What is the reaction with Mn2+ ions as the catalyst and reacting C2O4 2- and MnO4 -?

A

2MnO4 - + 5C2O4 2- + 16H+
=>
2Mn2+ + 10CO2 + 8H2O

54
Q

What are the 2 steps involved?

A

4Mn2+ + MnO4- + 8H+ => 5Mn3+ + 4H2O

2Mn3+ + C2O4- => 2Mn2+ + 2Co2

55
Q

How do we use the calorimeter?

A

= add appropriate ligand to intensify colour
= make up solutions of known concentrations
= measure absorption or transmission
= plot graph of absorption against concentratio
= measure absoroption of unknown and compare

56
Q

What does the coloured filter do?

A

= allow wavelengths of light that are most likely to be absorbed by the coloured solution

57
Q

What is the colour of [Co(H2O)6]2 +

A

=pink

58
Q

What is the reaction of [Co(Nh3)6]2+ when adding o2?

A

[Co(Nh3)6]3+ +e-
= goes from yellow to brown

59
Q

What is the reaction when [Co(H2O)6]2+ and 6 moles of ammonia?

A

= [Co(Nh3)6]2+ and 6 water

60
Q

What are some metal complexes more stable than others?

A

= entropy has increased- there is more disorder,
= more moles on the product side, so more stable

61
Q

What is the colour of [Co(Nh3)6]2+?

A

= yellow

62
Q

What is the colour of [Co(Nh3)6]3+?

A

= brown

63
Q

What kind of curve is the autocatalyst curve?

A

= s shaped
[MnO4-] and time

64
Q

For monodentate ligands how many moles do we use?

A

= the moles of 6 but, if it is partial only 4, such as copper complexes with ammonia

65
Q

For bidentate ligands how many moles do we us?

A

6/2 3, as bidentate ligands can each form 2 dative covalen bonds as there are 2 lone pairs of electrons

66
Q

What is the side effect of cis platin?

A

= may attach to healthy DNA cells, and kill them, medical side effects

67
Q

What impurties posion the iron catalyst in the haber process?

A

= sulfur impurities

68
Q

How does spectphotometry work?

A

= visile light of increasing frequency passes through a sample of coloured complex ion, some light is absorbed
= amount of light absorbed is porportional to concentration of absorbing species and distance travelled throug solution
So there is not an energy transfer equal to
that of visible light.
= some complexes have pale solutions

69
Q

What happens with the redox tritratio between fe2+ ions and mno4- ions?

A

= titration is self indicating, significant colour change from reactant to product

70
Q

What is the equation for the redox tritration?

A

= Mno4- + 8h+ + 5Fe2+ forms
Mn2+ + 4H2O + 5fe3+

71
Q

What is the problem with the colour of the magnate?

A

= purple colour of magnate can make it difficult to see bottom of miniscus
= if magnate is in birutte, end point of tritration will be first permanent pink colour- colourless to pink

72
Q

What does copper aqeous react with ammonia general points?

A

= blue precipitate
= dissolves to form deep blue solution

73
Q

Why can magnate ion be detected?

A

= coloured ions

74
Q

What factors affecy the heterogenous catalysts?

A

= adsorption
= surface area
= impurities.

75
Q
A

second year a level chemistry (56 decks)

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