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Chemistry > Topic 15 Transition metals > Flashcards

Topic 15 Transition metals Flashcards

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1
Q

Transition metal

A

Stable ion with a partially filled d-subshell

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2
Q

Which two transition metals only have one electron in the 4s orbital

A

Chromium and Copper

An electron from the 4s orbital moves into the 3d orbital to create a more stable half full or full 3d subshell

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3
Q

Which two d-block elements are not transition metals

What ions do they form

A

Scandium and Zinc

Scandium form only 1 stable ion for Sc3+ - empty d-subshell

Zinc forms one stable ion of Zn2+ - full d-subshell

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4
Q

What is a complex ion

A

Where a central transition metal surrounded by ligands bonded by coordinate bonds

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5
Q

Ligand

A

is an ion/atom or molecule that has at least 1 lone pair of electrons

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6
Q

What are Monodentate ligands

A

Ligands that have 1 lone pair of electrons

H2O, NH3, Cl-, OH-

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7
Q

What are Bidenetate ligands

A

Ligand which have 2 lone pairs of electrons

Dicarboxylate ion, NH2CH2CH2NH2

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8
Q

Multidentate Ligands

Give an example

A

LIgands that have more than 1 coordinate bond

EDTA4- can for 6 coordinate bonds with one metal ion

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9
Q

complexes with six ligand coordinate bonds have a WHAT shape

What is the bond angle

A

Octahedral shape

90° bond angle

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10
Q

Transition metal complex can bond to how many Cl- ions

What shape does this give

What bond angle is this

A

4 coordinate bonds

Tetrahedral shape

109.5° bond angle

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11
Q

Which compound has 4 ligands bonded but doesn’t have a tetrahedral shape

What is it’s bond angle

A

cis-platin

Has a square planar shape due to there being two lone pairs

Bond angle of 90°

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12
Q

What shape is haemoglobin

What type of ligand bonds to form it

A

Octahedral

Made from a multidentate ligand

4 of the nitrogen come from the multidentate ligand - haem

1 of the coordinate bonds comes from large protein called globin

Final coordinate bond comes from either oxygen/water

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13
Q

How does haemoglobin carry oxygen in the blood

A

oxygen substitutes the water ligand in the lungs where the oxygen concentration is high forming oxyhaemoglobin

THen oxyhaemoglobin gives up oxygen to a place where it is needed, water takes its place

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14
Q

What is the problem with carbon monoxide and haemoglobin

A

Water ligand is replaced by carbon monoxide ligand

However, the bond with carbon monoxide is so strong it cannot be replaced with oxygen/water again

So oxygen cannot be transported from the lungs

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15
Q

Which type of ligand can show optical isomerism

A

Octerherdral complexes with 3 bidentate ligands

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16
Q

What shape of complex can have cis-trans isomerism

A

octahedral complexes with 4 ligands of the same type and 2 ligands of a different type

To different ligands opposite another - trans

Two ligands are adjacent - cis

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17
Q

Describe the difference between cis-platin and trans-platin

A

Cis- on the same side of the platinum

Trans - on the opposite side of the platinum

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18
Q

Why can transition metals have variable oxidation states

A

due to the electrons in 3d and 4s subshell being close together

as a result, electrons are gained and lost using a similar amount of energy when they form ions

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19
Q

When does the d-orbital split

Why does this produce a colour

A

when ligands bond with the central metal ions

It causes some orbitals to gain energy- an energy gap is created - ΔE

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

In order for this to happen energy must equal ΔE

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20
Q

What is the size of ΔE dependent on

A

central metal ion and it’s oxidation state

Type of ligand

Coordination number

21
Q

How do complementary colours link to ΔE

A

The frequencies that are absorbed = ΔE

We then view a complementary colour for the light which is reflected

22
Q

Why do some d-block elements not produce a complimentary colour

A

For complexes where there are full or empty 3d subshells, no electrons migrate to a higher energy level

These complexes are white

23
Q

How does redox potential link to transition metals

A

The least stable ions have the largest redox potential

are more likely to be reduced

Positive = reduced

24
Q

What are the standard conditions for measuring redox potentials

A
  • 298K
  • 100kPa
  • 1 moldm-3
25
Q

What are the 4 oxidation states of vanadium and the colours

A

V2+ - Violet

V3+ - Green

VO2+ - Blue

VO2+ - Yellow

26
Q

What element can we use to reduce vanadium

How far can we reduce vanadium

A

VO2+ ⇢ VO2+ = yellow to blue

VO2+ ⇢ V3+ = blue to green

V3+ ⇢ V2+ = green to violet

27
Q

What are the 4 chromium complexes you need to know about

A

Cr2O72+ = Orange

CrO42- = Yellow

Cr3+ = Green

Cr2+ = Blue

28
Q

What can use to reduce chromium

How far can you reduce it

What is the problem however

A

Zinc

From Cr2O72+ ⇢ Cr3+ = Orange to green (what happens in oxidation of alcohols)

Cr3+ ⇢ Cr2+ = Green to blue

Cr2+ is very unstable and will readily oxidise back to Cr3+ with oxygen in the air

29
Q

What can you use to oxidise Chromium

How far can you oxide it

A

Hydrogen peroxide (H2O2)

From Cr3+ to Cr2O72- = from green to orange

30
Q

Which two ions of Chromium exist within equilibrium

A

CrO42- and Cr2O72-

Adding acid to yellow CrO42- creates orange Cr2O72-

31
Q

Which complexion of Chromium is Amphoteric

What colour is it

How is it made

A

[Cr(H2O)3(OH)3] - Which is a green/grey precipitate

It can be made by adding 3OH-/3NH3 to green [Cr(H2O)6]3+

32
Q

When [Cr(H2O)3(OH)3] reacts with acid or alkali, what type of reaction occurs

A

acid/base reaction

33
Q

What happens when you add excess ammonia to [Cr(H2O)3(OH)3]

What would be the colour change

What type of reaction is this

A

[Cr(H2O)3(OH)3] + 6NH3 ⇢ [Cr(NH3)6]3+ + 3H2O + 3OH-

Goes from green/grey solid to purple

Ligand exchange reaction

34
Q

What colour is Copper2+ in aqueous solutions

What is it’s structure

A

Blue

[Cu(Η2Ο)6]2+

35
Q

What colour is Iron 2+ in aqueous solution

What is it’s structure

A

[Fe(Η2Ο)6]2+

Pale green coloured

36
Q

What colour is Iron 3+ in aqueous solution

What is it’s structure

A

Yellow

[Fe(Η2Ο)6]3+

37
Q

What is the colour of Cobalt 2+ in aqueous solution

What is it’s structure

A

Pale pink

[Co(Η2Ο)6]2+

38
Q

What is the colour of the precipitate when 2NH3/2OH- are added to [Cu(Η2Ο)6]2+

What is it’s structure

A

Pale blue precipitate

Cu(OH)2(Η2Ο)4

39
Q

What is the colour of the solution produced when 6NH3 is added to Cu(OH)2(Η2Ο)4

What is the structure of the product

A

Dark blue solution

[Cu(ΝΗ3)4(Η2Ο)2]2+

40
Q

What is the colour of the precipitate when 2NH3/2OH- are added to [Fe(Η2Ο)6]2+

What is the structure of the product

A

Dirty green precipitate

Fe(OH)2(Η2Ο)4

41
Q

What is the colour of the precipitate when 3NH3/3OH- are added to [Fe(Η2Ο)6]3+

What is the structure of the product

A

Orange precipitate

Fe(OH)3(Η2Ο)3

42
Q

What is the colour of the precipitate when 2NH3/2OH- are added to [Co(Η2Ο)6]2+

What is it’s structure

A

Blue precipitate - turns brown after a while

Co(OH)2(Η2Ο)4

43
Q

What is the colour of the solution when Co(OH)2(Η2Ο)4 reacts with 6NH3

What is the structure of the product

What type of reaction is it

A

Brown/Yellow solution

Co(NH3)62+

Ligand exchange

44
Q

What would be the colour change associated with this reaction

[Cu(Η2Ο)6]2+ +4Cl- ⇢ [CuCl4]2−

What type of reaction is it

A

from blue to yellow

ligand exchange and coordination number

45
Q

What would be the colour change associated with this reaction

[Co(Η2Ο)6]2+ +4Cl- ⇢ [CoCl4]2−

What type of reaction is it

A

Pink to blue

ligand substitution and coordination number

46
Q

substitution of a monodentate ligand by a bidentate or multidentate ligand leads to a more stable complex ion, why?

A

the large positive increase in ΔSsystem

Due to more molecules being in multidentate ligands than mono/bidentate ligands

47
Q

Describe the contact process

Which transition metal is used as a catalyst

A

To produce sulphuric acid

Vanadium is the catalyst

SO2 + V2O5 ⇢ SO3 + V2O4

V2O4 + 0.5O2 ⇢ V2O5

48
Q

Which transition metal catalyses the reaction between I− and S2O82− ions

A

Fe2+

  • S2O82− + 2Fe2+ ⇢ 2Fe3+ + SO42-
  • 2Fe3+ + I- ⇢ 2Fe2+ + I2
49
Q

What ion is used in autocatalysing the reaction between MnO4− and C2O42− ions

A

Mn2+

  • MnO4− + 8H+ + 4Mn2+ ⇢ 5Mn3+ + 4H2O
  • 2Mn2+ + C2O42− ⇢ Mn2+ + 2CO2

Chemistry (12 decks)

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