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Chem Unit 3 > 3.4 Transition Metals > Flashcards

3.4 Transition Metals Flashcards

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1
Q

transition metal??

A

a d-block element that forms one or more stable ions w/ partially filled d-orbitlas

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2
Q

which 2 elements in d-block of periodic table are not technically transition metals??

A

scandium & zinc
they do not form ions w/ an incomplete d-subshell

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3
Q

which 2 elements in periodic table are exceptions to rule that the 4s orbital is filled before 3p orbital??

A

chromium & copper, 4s ortibals only fill w 1 e- as this gives them more stable configurations in the 3d orbital
chromium: [Ar]4s1,3d5
copper: [Ar]4s1, 3d10

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4
Q

some general properties of transition metals??

A

-they have variable oxidation states
-form complex ions
-form coloured ions in solution
-catalyse the rcts either as elements or in compounds

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5
Q

examples of transition metals that have variable oxidation states??

A

Fe2+ & Fe3+
Cu+ & Cu2+
Cr2+ & Cr3+

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6
Q

why do transition metals have variable oxidation states??

A

variable oxidation states arise because the electrons in the 4s & 3d orbitals have very similar energies meaning that a relatively similar amnt oof eneergy is req to gain or lose diff numbers of electrons

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7
Q

most common oxidation states of Cr??

A

+2
+3
+6

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8
Q

most common oxidation states of Mn??

A

+2
+4
+7

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9
Q

most common oxidation states of Cu??

A

+1 & +2

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9
Q

what are the most common ox states of Fe??

A

+2
+3

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10
Q

most common oxidation states of Co??

A

+2
+3

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11
Q

what colour are aq solns of compounds containing Cr3+ ions??

A

green

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12
Q

what colour are aq solns of compounds containing CrO42- ions??

A

yellow

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13
Q

what colour are aq solns of compounds containing Cr2O72- ions??

A

orange

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14
Q

what colour are aq solns of compounds containing MnO4- ions??

A

purple

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15
Q

what colour are aq solns of compounds containing Co2+ ions??

A

pink

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16
Q

what colour are aq solns of compounds containing Fe2+ ions??

A

green

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17
Q

what colour are aq solns of compounds containing Fe3+ ions??

A

brown

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18
Q

what colour are aq solns of compounds containing Cu2+ ions??

A

blue

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19
Q

ligand??

A

a ligand is an ion or molecules that bonds to a central metal atom to form a complex ion

20
Q

what type of bonding is incolved in the formation of metal complex ions??

A

dative(coordinate) bonding
this type of covalent both in which both electrons begin shared are donated to teh same atom

21
Q

complex ion??

A

a central metal ion surrounded by ligands

22
Q

“aq solns of transition metal ions are usually ——”

A

coloured

23
Q

coordinate number??

A

the number of dative bonds formed w/ a central metal ion

24
Q

why do transition metals form coloured complexes??

A

when visible light hits a transition metal ion electrons are excited to higher energy levels, some freqs of the visible light are absorbed when electrons jump to higher energy orbitals. the rest of the freqs of visible light are transmitted or reflected, these freqs combine to make the complement of the colour of absorbed freqs creating colours of the complexes

25
Q

what can lead to a colour change in a transition metal??

A

-change in oxidation number of the ion
-chnage in the ligand
-change in coordination number of the complex

26
Q

what is the shape of the [CrCl4]- complex??

A

tetrahedral
bond angle: 109.5

27
Q

what is the shape of the [Cr(NH3)6]3+ complex??

A

octahedral
bond angle: 90

28
Q

what is the shape of the [Cu(NH3)4(H2O)2]2+ complex?

A

octahedral
bond angle: 90

29
Q

what is a ligand exchange rctn??

A

a ligand exchange is a chemical rctn involving the replacement of ligands in a complex by a diff set of ligands:
[Cu(H2O)6]2+ + 4NH3 –> [Cu(NH3)4(H2O)2]2+ + 4H2O

30
Q

what is the eqn & the observations for the ligand exchange rctn bet copper hexaaqua ions & ammonia??

A

blue soln forms a light blue ppt, this dissolves in excess ammonia to form a dark blue soln
blue[Cu(H2O)6]2+(aq) + 2NH3(aq) –> light blue pptCu(H2O)4(OH)2 + 2NH4+(l)
light blue pptCu(H2O)4(OH)2 + 2NH3(aq) –> dark blue soln[Cu(NH3)4(H2O)2]2+(aq) + 2OH- + 2H2O

31
Q

what is the eqn & the observations for the ligand exchange rctn bet copper hexaaqua ions & chloride ions??

A

blue soln forms a yellow solution
blue[Cu(H2O)6]2+(aq) + 4Cl-(aq) –> yellow[CuCl4]2-(aq) + 6H2O(l)

32
Q

what is the eqn & the observations for the ligand exchange rctn bet cobalt hexaaqua ions & chloride ions??

A

the pink soln forms a dark blue soln
pink[Co(H2O)6]2+(aq) + 4Cl-(aq) <–> dark blue[CoCl4]2-(aq) + 6H2O(l)

33
Q

What colour are the compounds [CoCl4]2- & [CuCl4]2- ??

A

[CoCl4]2- –> Blue
[CuCl4]2- –> Green

34
Q

What colour are the compounds [Co(H2O)6]2+ & [Cu(H2O)6]2+ ??

A

[Co(H2O)6]2+ —> Pink
[Cu(H2O)6]2+ —> Blue

35
Q

what colour is the compound [Cu(NH3)4(H2O)2]2+ ??

A

Blue

36
Q

what is the difference bet a homogeneous & a heterogeneous catalyst??

A

homogeneous catalyst is in the same phase as the rctnts & the catalysed rctn takes place via intermediate species
hetergeneous catalyst is in a diff phase to the rctnts & the rctn occurs on the surface of the catalyst

37
Q

why do transition metals make good homogeneous catalysts??

A

transition metals have variable oxidation states making them good homogeneous catalysts, the variable oxidation states mean they are able to oxidise & reduce reactant & intermediates to form the desired products

38
Q

why do transition metals make good heterogeneous catalysts??

A

using the 3d & 4d electrons of the atoms on the catalyst surface, transition metals can form weak bonds w/ rctnts making them more reactive

39
Q

what catalyst is used in the hydrogenation of alkenes?? is it homogeneous or heterogeneous??

A

nickel
heterogeneous

40
Q

what catalyst is used in the haber process?? is it homogeneous or heterogeneous??

A

iron
heterogeneous

41
Q

contact process??

A

an industrial process used to make sulfuric acid, it is made by oxidising sulfur dioxide in the presence of a solid catalyst, sulfur trioxide is then reacted w/ water to form sulfuric acid

42
Q

what conditions req for the contact process??

A

temp 450C
Vanadium oxide catalyst (V2O5)
pressure 2 atm

43
Q

two eqns showing how vanadium acts as a catalyst in the contact process??

A

SO2 + V2O5 –> SO3 + V2O4
V2O4 + 1/2O2 –> V2O5

44
Q

what catalyst is used in the decomposition of hydrogen peroxide?? is it homogeneous or heterogeneous??

A

manganese (IV) oxide
homogeneous

45
Q

eqn for the rctn of Cr(III) ions w/ excess NaOH??

A

purple [Cr(H2O)6]3+ + 6OH- –> green[Cr(OH)6]3- + 6H2O

46
Q

give eqn of the rctn of Fe(II) ions w/ excess NaOH??

A

green soln forms a green ppt
green soln[Fe(H2O)6]2+ + 2OH- –> green ppt Fe(H2O)4(OH)2 + 2H2O

47
Q

give eqn of the rctn of Fe(III) ions w/ excess NaOH??

A

orange soln forms a brown ppt
orange soln[Fe(H2O)6]3+ + 3OH- –> brownppt Fe(H2O)3(OH)3 + 3H2O

48
Q

Give the eqn for the rctn of Cu(II) ions w/ excess NaOH??

A

blue[Cu(H2O)6]2+ + 2OH- –> blueCu(H2O)4(OH)2 + 2H2O

Chem Unit 3 (9 decks)

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