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chemistry A-level 2 > transition metal > Flashcards

transition metal Flashcards

1
Q

What are transition metals

A

elements in the d-block of the periodic table with a partially filled d-orbital. they lose electrons to form positive ions with the s-orbital electrons being removed first

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2
Q

physical properties of transition metals

A
  • atomic radius
  • high densities
  • high melting and boiling point
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3
Q

chemical properties of transition metals

A
  • can form different ions/complexes
  • form coloured compounds and solutions
  • used as catalysts in industrial processes
  • typically harder/ more dense than other metals
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4
Q

what are complexes

A

These form from transition metals, consisting of a central metal ion or bonded to one or more ligands by cooridnate bonds

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5
Q

what are ligands

A

molecules or inos with a lone electron pair that can form a cooridante bond to the central metal ions by donating this electron pair

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6
Q

common ligands include

A
  • Cl-
  • H2O
  • NH3
  • CN-
  • OH-
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7
Q

What is the coordination number equal to

A

equal to the number of coordinate bonds formed around the central metal ion

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8
Q

how are colours produced in complexes

A
  • when a transition metal ion forms a “complex” (e.g. in water) the d orbitals split in energy.
  • particular wavelengths of visible light are absorbed to “excite” to the higher energy level.
  • light that is not absorbed determines the colour we observe
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9
Q

energy equation

A

E = h f

E = energy (J)
f = frequency (Hz)
h = planck’s constant - 6.63 x 10-34 Js

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10
Q

frequency equation

A

f = c / w

f = frequecny (Hz)
c = speed of light - 3 x108 ms-1
w = wavlength (m)

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11
Q

energy and frequency equation mixed

A

E = h c / w

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12
Q

absorption equation

A

A = E c l

A = absorption
E = absorption coefficient (constant)
c = concentration
l = path length (constant)

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13
Q

coordination number 2

A

linear shape
e.g. [Ag(NH3)2]+

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14
Q

coordination number 4

A

tetrahedral
[CuCl4]2-

square planar
[Ni(CN)4]2-

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15
Q

coordination number 6

A

octahedral
[Cu(H2O)6]2+

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16
Q

what are monodentate ligands

A

a species that donates 1 lone pair of electrons to the central metal ion
e.g. NH3, H2O, Cl-, CN-, OH-

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17
Q

what are bidentate ligands

A

a species that can form 2 coordinate bonds to the metal ion
e.g. 1,2-diaminoethane - NH2CH2CH2NH2
e.g. ethanedioate - C2O4 2-

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18
Q

what are multidentate ligands

A

these ligands form many coordinate bonds the central metal ion
e.g. EDTA 4-

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19
Q

EDTA

A

the acid is normally in an alkali buffer solution to ensure it is the anion form. all the acid COOH groups lose their H+ to form the anion EDTA 4-

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20
Q

uses of EDTA

A
  • bind metal ions
  • detergents
  • food
  • medicine
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21
Q

how does EDTA bind metal ions

A

aka Chelating agent
So EDTA decreases the conc. of metal ions in solutions by binding them into a complex

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22
Q

how is EDTA used as a detergent

A

binds Ca and Mg to reduce the hardness of water

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23
Q

how is EDTA used in food

A

acts as a stabiliser to remove metal ions that might catalyse the oxidation of the product

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24
Q

how is EDTA used in medicine

A

added to food samples to prevent clotting and used to treat patients form lead and mercury poisoning

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25
cis- trans isomerism
shown by octahedral complexes with different types of unidentate ligands - trans isomer has two of the same ligands opposite each other - cis isomer has them next to each other
26
ligand substitution reactions
Ligands NH3 and H2O are similar in size and both uncharged. They can be exchanged without a change in coordination number via a ligand substitution reactions
27
[Cu(H2O06]2+ + Cl-
[Cu(H2O)6]2+ + Cl- <=> [CuCl4]2- + 6H2O light blue solution -> technically yellow but always appears as green
28
[Cu(H2O)6]2+ + 6NH3
[Cu(H2O)6]2+ + 6NH3 <=> [Cu(NH3)4(H2O)2]2+ + 4H2O light blue solution -> ppt in between -> deep blue solution
29
[Co(H2O)6]2+ + 4Cl-
[Co(H2O)6]2+ + 4Cl- <=> [CoCl4]2- + 6H2O pink solution -> blue solution
30
reagents needed to identify solutions containing transition metal ions
- add NaOH - add NH3 - add Na2CO3 - carbonate ions CO3 2-
31
add NaOH to [Cu(H2O)6]2+
[Cu(H2O)6]2+ + 2OH- -> Cu(H2O)4(OH)2 + 2H2O light blue solution -> blue ppt
32
add NaOH to [Fe(H2O)6]2+
[Fe(H2O)6]2+ + 2OH- -> Fe(H2O)4(OH)2 + 2H2O pale green solution -> green ppt
33
add NaOH to [Fe(H2O)6]3+
[Fe(H2O)6]3+ + 3OH- -> Fe(H2O)3(OH)3 + 3H2O orange brown solution -> orange brown ppt
34
add NaOH to [Al(H2O)6]3+
[Al(H2O)6]3+ + 3OH- -> [Al(OH)6]3- + 3H2O light blue solution -> blue ppt
35
add NaOH to Al(H2O)3(OH)3
Al(H2O)3(OH)3+ + 3OH- -> [Al(OH)6]3- + 3H2O white ppt -> colourless solution redissolves
36
add NH3 to [Cu(H2O)6]2+
[Cu(H2O)6]2+ + 2NH3 -> Cu(H2O)4(OH)2 + 2NH4+ light blue solution -> blue ppt
37
add NH3 to [Fe(H2O)6]2+
[Fe(H2O)6]2+ + 2NH3 -> Fe(H2O)4(OH)2 + 2NH4+ green solution -> green ppt
38
add NH3 to [Fe(H2O)6]3+
[Fe(H2O)6]3+ + 3NH3 -> Fe(H2O)3(OH)3 + 3NH4+ orange brown solution -> brown ppt
39
add NH3 to [Al(H2O)6]3+
[Al(H2O)6]3+ + 3NH3 -> Al(H2O)3(OH)3 + 3NH4+ colourless solution -> white ppt (does not redissolve in excess ammonia)
40
add Na2CO3 [Cu(H2O)6]2+
[Cu(H2O)6]2+ + CO32- ->CuCO3 + 6H2O light blue solution -> green ppt
41
add Na2CO3 [Fe(H2O)6]2+
[Fe(H2O)6]2+ + CO32- ->FeCO3 + 6H2O green solution -> green ppt
42
add Na2CO3 2 [Fe(H2O)6]3+
2 [Fe(H2O)6]3+ + 3CO32- -> 2Fe(H2O)3(OH)3 + 3H2O + 3CO2 brown solution -> brown ppt & bubbles
43
add Na2CO3 2 [Al(H2O)6]3+
2 [Al(H2O)6]3+ + 3CO32- -> 2Al(H2O)3(OH)3 + 3H2O + 3CO2 colourless solution -> white ppt & bubbles
44
how many possible oxidation states can vanadium have
4 - They all produce a different coloured compound. These different species are produced from the oxidation of vanadium by zinc in an acidic solution
45
what is the vanadium ion for the oxidation state of +5
VO2 + yellow
46
what is the vanadium ion for the oxidation state of +4
VO 2+ blue
47
what is the vanadium ion for the oxidation state of +3
V 3+ green
48
what is the vanadium ion for the oxidation state of +2
V 2+ violet
49
What determines whether a transition metal is oxidised or reduced
pH Reduction = acidic conditions are required Oxidation = alkaline osluiton, react with water to produce OH-
50
tollens reagent
silver complex [Ag(NH3)2]+ is reduced by aldehydes to form silver atoms RCHO + 2[Ag(NH3)2]+ + 3OH- -> RCOO- + 2Ag + 4NH3 + 2H2O
51
redox titrations MnO4 - forming Mn2+
MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O
52
redox titrations Fe2+ forming Fe3+
Fe2+ -> Fe3+ + e-
53
redox titrations C2O42- forming 2CO2
C2O42- -> 2CO2 + 2e-
54
why are trnasition metals good catalysts
due to their variable oxidation states. electrons are transferred to produce a reactive intermediate and speed up the reaction rate
55
what is a heterogeneous catalyst
in a different phase from the species in the reaction. typically a solid metal catalyst wwith liquid/gas. for a solid catalyst, reactions occur at the surface
56
example of a heterogeneous catalyst The contact process overall equation: intermediates:
2SO2 + O2 <=> 2SO3 2SO2 + 2V2O5 -> 2SO3 + 2V2O4 2V2O4 + O2 -> 2V2O5 vanadium is reduced form +5 to +4 and is reformed in its original oxidation states
57
example of a heterogeneous catalyst The haber process overall equation:
N2 (g) + 3H2 (g)<=> 2NH3 (g) Fe catalyst
58
example of a heterogeneous catalyst HYdorgention of alkenes overall equation:
C2H4 (g) + H2 (g) <=> C2H6 (g) Ni catalyst
59
adsorption with a solid catalyst
adsorbs molecules onto an active site on the catalyst's surface. The active sites increase the proximity of molecules and weaken the covalent bonds in the molecules so that reactions occur more easily and rate is increased
60
what does the strength of adsorption on
The type of catalyst affects the rate of reaction. iron, cobalt, and nickel make the best catalysts as they are cheap and increase the rate of reaction the most out of period 4 tm
61
catalytic poisoning
unwantd gas adsorbs very storgnyl onto a catltlyste - the acitve site is blocked, reducing the catalyst effectiveness
62
tungsten involvement in catalytic posioning
bonds strongly to the reactant molecules. adsorption is so strong that molecules are unable to leave the surface, and the catalyst is poisoned and rendered useless
63
Silver's involvement in catalytic poisoning
adsorbs to weakly to hold molecules on the surface long enough for a reaction to occur
64
homogenous catalysts
catalysts that are in the same phase to he species in the reaction. reaction proceeds through an intermediate stage
65
homogenous catalysts peroxidsulfate ions and iodide ions overall equation: intermediate reactions:
S2O8 2- + 2I- -> I2 + 2SO4 2- S2O8 2- + 2Fe 2+ -> 2Fe3+ + 2SO4 2- 2Fe3+ + 2I- -> 2Fe2+ + I2
66
homogenous catalysts peroxidsulfate ions and iodide ions reaction
- witohut a catalyst these -ve ions would repel and not react - reaction is slow -as it has a high activation energy due to -ve ions
67
autocatalysis
product can act as a catalyst for the reaction. over time amount of product increases, rate of reaction increases as it becomes catalysed
68
example of autocatalysis reaction 2MnO4 - -> 2Mn 3+ overall: intermediate reactions:
2MnO4 - + 16H+ + 5C2O4 2- -> 2Mn2+ + 8H2O + 10Co2 4Mn2+ + MnO4 - + 8H+ - 5Mn 3+ + 4H2O 2Mn3+ + C2O4 2- -> 2CO2 + 2Mn 2+
69
autocatalysis reaction of 2MnO4 - -> 2Mn 3+
- small amount of inital heating, to produce Mn 2+ ions - after this, rate of reaction increases without further heating - reaction monitored using a colorimeter as MnO4 - is purple in solution
70
autocatalysis graph
1. gradient is low as the reaction is slow as it has a high activation energy 2. gradient gets steeper as Mn2+ forms which is the autocatalyst 3. rate increases as the continued production of Mn2+ increases 4. Mno4- is used up - gradient decrease as it approaches the axis

chemistry A-level 2 (17 decks)

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