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chemistry > 23 transition metals > Flashcards

23 transition metals Flashcards

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1
Q

how do you define a transition element?

A

an element that forms at least one stable ion with a partially filled d sub shell

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2
Q

why is scandium not a transition element?

A

only forms Sc3+ which makes a non-partially filled d sub shell (3d0)

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3
Q

give 4 features of a transition element

A
  1. forms complex ions
  2. coloured ions
  3. catalytic properties
  4. variable oxidative states
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4
Q

define a co-ordinate bond

A

a shared pair of electrons where both electrons come from the same atom

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5
Q

define a ligand

A

a lone pair of electrons which can form a co-ordinate bond with a transition metal ion

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6
Q

define coordination number

A

number of coordinate bonds formed

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7
Q

define complex ion

A

central atom/ion surrounded by ligand

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8
Q

what is a:
monodentate ligand?
bidentate ligand?
multidentate ligand?

A

monodentate- each ligand forms 1 coordinate bond
bidentate- each ligand forms 2 coordinate bonds
multidentate ligand- each ligand forms 2 or more coordinate bonds

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9
Q

what are 5 monodentate ligands?

A

:H2O
:NH3
:Cl
:OH-
:CN

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10
Q

what are 2 bidentate ligands?

A

1,2-diaminoethane
ethanedioate ion

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11
Q

what is the structural formula for 1,2-diaminoethane?

A

NH2CH2CH2NH2

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12
Q

what does an ethanedioate ion look like?

A

2 carbons
double bond O attached to each
single bond :O- attached to each

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13
Q

what are 4 common shapes transition metal complexes can form?

A

octahedral
linear
square planar
tetrahedral

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14
Q

how many bonds does each shape transition metal complexes can form have?

A

octahedral- 6
linear- 2
tetrahedral- 4
square planar- 4

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15
Q

give 2 examples of complexes that form octahedral shapes

A

[Cu(H2O)]2+
[Co(NH3)6]2+

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16
Q

give an example of a complex with a tetrahedral shape

A

[CoCl4]2-

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17
Q

why can’t transition metals with Cl ligand be octahedral?

A

because Cl ions are large and only 4 can fit around the transition metal

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18
Q

give an example of a complex with a square planar shape

A

[Ni(CN)4]2-

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19
Q

give the structural formula of the complex that forms an octahedral shape with multidentate ligands

A

[Ni(NH2CH2CH2NH2)3]2+

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20
Q

name a hexadentate ligand

A

EDTA4-

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21
Q

what shape does EDTA4- form in a complex?

A

octahedral

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22
Q

what is a ligand substitution reaction?

A

when a ligand attached to the transition metal ion is replaced by a different ligand

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23
Q

give the equation to show how the complex [CU(H2O)6]2+ can be turned into [CU(H2O)3(NH3)3]2+

A

[Cu(H2O)6]2+ + 3NH3 –> [Cu(H2O)3(NH3)3]2+ + 3H2O

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24
Q

give the equation to show how [Cu(H2O)6]2+ can be turned into [CuCl4]2-

A

[Cu(H2O)6]2+ + 4Cl- –> [CuCl4]2- + 6H2O

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25
Q

what is the chelate effect?

A

when a monodentate ligand is substituted by a bidentate ot multidentate ligand and a large increase of entropy occurs

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26
Q

why does a large increase of entropy occur when a monodentate ligand gets replaced by a bidentate or a multidentate ligand?

A

because there is an increase in molecules on the right hand side of the equation

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27
Q

define stereoisomer

A

same structural formula but different arrangement of atoms in space

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28
Q

what are the two types of stereoisomerism transition metals can display?

A

geometrical and optical

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29
Q

what is a cis isomer in an octahedral complex?

A

where alike ligands are arranged next to each other at a 90° angle

30
Q

what is a trans isomer in an octahedral complex?

A

where alike ligands are arranged opposite from each other at a 180° angle

31
Q

what is a cis isomer in a square planar complex?

A

if alike ligands are next to each other

32
Q

what is a trans isomer in a square planar complex?

A

if alike ligands are apposite to one another

33
Q

what is the structural formula for cisplatin?

A

[PtCl2(NH3)2]

34
Q

what is cisplatin?

A

a very effective anti-caner drug when it is a cis isomer

35
Q

how does cisplatin work?

A

binds to cancerous cells to stop cell replication
(Cl- on cisplatin are substituted for N on guanine)

36
Q

what are the colours that make up white light?

A

red
orange
yellow
green
blue
indigo
violet

37
Q

which colours in white light have lower energy?

A

red orange yellow

38
Q

which colours in white light have higher energy?

A

blue indigo violet

39
Q

why are most transition metal compounds coloured?

A

partially filled d sub shell absorbs some of the colours from white light and transmits other colours

40
Q

what do the electrons in the d orbital need to be excited?

A

energy from white light

41
Q

where are the d orbital electrons excited to and from?

A

ground state to excited state

42
Q

how do you calculate the change in energy absorbed by electrons?

A

ΔE = hv
or
ΔE = h c/λ

43
Q

what do the letters in ΔE = hv stand for?

A

ΔE - change in energy
h - Planck’s constant (J s)
v- frequency of light ( s-1)

44
Q

what do the letters in ΔE = h c/λ stand for?

A

ΔE - change in energy
h - Planck’s constant (J s)
c - speed of light
λ - wavelength of light (m)

45
Q

how many m is 1nm

A

1x10^-9

46
Q

what does big e BIV abs mean?

A
  1. transition metal has large ΔE between d sub shells
  2. high energy light
  3. will be absorbed to excite electrons
  4. ROY will be transmitted to make compound look red
47
Q

what does small e ROY abs mean?

A
  1. transition metal has a small ΔE between d sub shells
  2. low energy light
  3. will be absorbed to excite electrons
  4. BIV will be transmitted to make compound look blue
48
Q

what changes could alter the colour of a compound?

A
  1. change in Ligands
  2. change in Oxidation states
  3. change in Coordination number
  4. change in Shape of complex
49
Q

what apparatus can you use to measure the amount of light absorbed?

A

colorimeter

50
Q

how does a colorimeter work?

A
  1. light source shines a light of specific frequency through solution
  2. some light absorbed some light transmitted
  3. transmitted light hits the detector
  4. detector gives reading for the amount of light which passed through
51
Q

what does a 1.0 transmittance reading mean in colorimetry?

A

that all the light passed through the sample and none was absorbed

52
Q

what can colorimetry also be used to determine?

A

an unknown concentration of a transition metal ion

53
Q

how can colorimetry determine an unknown concentration of a transition metal ion?

A
  1. measure absorbance of known concentrations
  2. plot graph: absorbance against concentration
  3. read value of conc for measured absorbance from graph
54
Q

what physical factor when doing a colorimetry test affects the amount of absorption?

A

length of container affects distance light has to travel

55
Q

what does a filter do in colorimetry?

A

only lets one colour of light through sample

56
Q

what does placing a cuvette filled with water into colorimeter and setting to zero do?

A

ensures accuracy and negates absorbance due to solvent

57
Q

what is a catalyst?

A

a substance that increases the rate of reaction without being used up

58
Q

how does a catalyst work?

A

by providing an alternative pathway with a lower activation energy

59
Q

when a catalyst is added, which way does Ea move on a maxwell boltzmann distributon?

A

to the left

60
Q

what is a heterogeneous and a homogeneous catalyst?

A

heterozygous- where the catalyst is in a different phase to the reactants
homozygous- where the catalyst is in the same phase as the reactants

61
Q

what state is a heterogeneous catalyst usually in?

A

solid

62
Q

list the steps of a heterogeneous catalyst

A
  1. reactants adsorb onto surface of catalyst on active site
  2. reaction occurs on surface of catalyst (bonds weaken)
  3. products desorb from the surface of catalyst
63
Q

what does adsorb mean?

A

stick

64
Q

what ate 3 heterogeneous catalyst examples?

A
  1. solid iron
    making ammonia in the haber process
  2. solid V2O5
    making sulfuric acid
  3. solid chromium (III)
    manufacture of methanol
65
Q

what is the equation that solid iron catalyses?

A

making ammonia in the haber process:
N2(g) + 3H2(g) ⇌ 2NH3(g)

66
Q

what is the equation that solid V2O5 catalyses?

A

making sulfuric acid in the contact process
SO2(g) + V2O5(s) ⇌ SO3(g) + VsO4(s)
2V2O4(s) + O2(g) ⇌ 2V2O5
2SO2(g) + O2(g) -> 2SO3
sulfuric acid formed by reacting with water

67
Q

what is the equation that solid chromium(III) catalyses?

A

manufacture of methanol
CO(g) + 2H2(g) -> CH3OH(g)

68
Q

what state are the majority of homogeneous catalysts and reactants in?

A

aqueous

69
Q

why can transition metals act as catalysts?

A

they have variable oxidation states

70
Q

why can’t group 1 metals be catalysts?

A

they only exist in one oxidation state

71
Q

give an example of a homogeneous catalyst

A

Fe2+

72
Q

what is the equation that Fe2+ catalyses?

A

S2O8^2- + 2I- -> 2SO4^2- +2Fe3+
2I- + 2Fe3+ -> I2 +2Fe2+
(all states aqueous)

chemistry (34 decks)

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