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Chemistry > Module 5.3 - Transition Metals > Flashcards

Module 5.3 - Transition Metals Flashcards

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1
Q

What happens in the reaction of aqueous Cu2+ ions and sodium hydroxide (and in excess)?

A

Blue solution to blue gelatinous precipitate
[Cu(H2O)6]+(aq) + 2OH-(aq) –> Cu{OH2)2(H2O)4 + 2H2O
no change in excess sodium hydroxide

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2
Q

What happens in the reaction between aqueous Cu2+ ions and ammonia (and in excess)?

A

Blue gelatinous precipitate formed that re-dissolves when excess ammonia to a dark blue solution
[Cu(H2O)6]2+(aq) + 2NH3(aq) –> Cu(OH)2(H2O)4 + 2NH4+(aq)
In excess ammonia (forms a dark blue solution)
forms [Cu(NH3)4(H2O)2]2+

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3
Q

What happens in the reaction between aqueous Fe2+ ions and sodium hydroxide (and in excess)?

A

Pale green solution containing Fe2+(aq) forms a green ppt, turning rusty brown at its surface on standing in air (as oxidised to Fe3+)
Fe2+(aq) + 2OH-(aq) –> Fe(OH)2(s)
No change when excess NaOH added

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4
Q

What happens in the reaction between aqueous Fe2+ ions and ammonia (and in excess)?

A

Dark green ppt formed
[Fe(H2O)6]2+(aq) + 2NH3(aq) –> Fe(OH)2(H2O)4 + 2NH4+(aq)
No change when excess NH3 added

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5
Q

What happens in the reaction between aqueous Fe3+ ions and sodium hydroxide (and in excess)?

A

Pale yellow solution containing Fe3+(aq) forms a rusty prown ppt - iron(III) hydroxide
Fe3+(aq) + 3OH-(aq) –> Fe(OH)3(s)
No change when excess NaOH added

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6
Q

What happens in the reaction between aqueous Fe3+ ions and ammonia (and in excess)?

A

Rusty brown ppt formed from a yellow solution
[Fe(H2O)6]3+(aq) + 3NH3(aq) –> Fe(OH)3(H2O)3 + 3NH4+
No change when excess NH3 added

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7
Q

What happens in the reaction between aqueous Mn2+ ions and sodium hydroxide (and in excess)?

A

Pale pink –> brown ppt forms which darkens in air as it oxidises
[Mn(H2O)6]2+(aq) + 2OH-(aq) –> Mn(OH)2(H2O)3 + 2H2O
Mn ion can be summarised to Mn(OH)2. Oxidation can be summaries by:
4Mn(OH)2 + O2 –> 2Mn2O3 + 4H2O
No change when excess NaOH added

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8
Q

What happens in the reaction between aqueous Mn2+ ions and ammonia (and in excess)?

A

Pale pink –> brown ppt forms, which darkens in air as it oxidises
[Mn(H2O)6]2+(aq) + 2NH3(aq) –> Mn(OH)2(H2O) + 2NH4+(aq)
No change when excess NH3 added

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9
Q

What happens in the reaction between aqueous Cr3+ ions and sodium hydroxide (and in excess)?

A

Violet solution (can appear green from impurities)–> green ppt forms, which re-dissolves in excess hydroxide
[Cr(H2O)6]3+(aq) + 3OH-(aq) –> Cr(OH)3(H2O)3 + 3H2O
In excess (forming a dark green solution):
Cr(OH)3(H2O)3 + 3OH-(aq) –> [Cr(OH)6]3- + 3H2O

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10
Q

What happens in the reaction between aqueous Cr3+ ions and ammonia (and in excess)?

A

Violet solution –> green ppt forms, which re-dissolves if excess ammonia added
[Cr(H2O)6]3+(aq) + 3NH3(aq) –> Cr(OH)3(H2O)3 + 3NH4+(aq)
In excess (forming a purple solution):
Cr(OH)3(H2O) + 6NH3(aq) –> [Cr(NH3)6]3+ + 3H2O + 3OH-(aq)

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11
Q

Explain the reaction of aqueous copper(II) nions and ammonia.

A

-contains [Cu(H2O)6]2+ complex ions which have a characteristic pale blue colour
-when NH3(aq) added, pale blue changes + deep blue solution formes
[Cu(H2O)6]2+(aq) + 4NH3(aq) ⇌[Cu(NH3)4(H2O)2]2+(aq) + 4H2O(l)
-4 H2O ligands replaced by 4 NH3 ligands
-product has 6 ligands so octahedral shape
-Cu-O longer than Cu-N so product has distorted octahedral shape
-2 changes observed in lab: on addition of small amount of NH3, pale blue ppt of copper(II) hydroxide forms as ammonia acts as alkali. When NH3 put into water forms NH4OH, which can partially ionise, releasing OH-
-on excess of NH3, pale blue ppt dissolves + deep blue solution formed containing [Cu(NH3)4(H2O)2]2+ ions

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12
Q

Explain the reaction of copper(II) ions and hydrochloric acid.

A

-when conc HCl added to CU2+(aq), pale blue solution initially forms green solution before finally turning yellow
-reaction exists in equilibrium + can be reversed by addition water to yellow solution to return to original blue colour
[Cu(H2O)6]2+(aq) + 4Cl- ⇌[CuCl4]2=(aq) + 6H2O(l)
pale blue solution ⇌yellow solution
-Cl ligands have stronger repulsions than water so fewer Cl fit around central metal ion
-goes from octahedral shape to tetrahedral shape
-can apply Le Chatelier’s principle as in equilibrium

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13
Q

What is a transition element?

A

A d-block element that has at least one ion with an incomplete d sub shell

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14
Q

Which d-block elements are not transition elements and why?

A
  • scandium: only forms Sc3+, where the d sub shell is empty

- zin: only forms Zn2+, where d sub shell is full

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15
Q

Which 2 transition metals don’t fit the trend of electron configuration and why?

A
  • chromium: 5 3d orbitals + 4s orbital all have 1 electron in, with none being full
  • copper: 3d orbitals are full, but there’s only 1 electron in the 4s orbital
  • in both, this electron arrangement means electron repulsion between outer electrons is minimised causing increased stability of the ions
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16
Q

What is the electron configuration of scandium?

A

1s2 2s2 2p6 3s2 3p6 4s2 3d1

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17
Q

What is the electron configuration of titanium?

A

1s2 2s2 2p6 3s2 3p6 4s2 3d2

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18
Q

What is the electron configuration of vanadium?

A

1s2 2s2 2p6 3s2 3p6 4s2 3d3

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19
Q

What is the electron configuration of chromium?

A

1s2 2s2 2p6 3s2 3p6 4s1 3d5

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20
Q

What is the electron configuration of manganese?

A

1s2 2s2 2p6 3s2 3p6 4s2 3d5

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21
Q

What is the electron configuration of iron?

A

1s2 2s2 2p6 3s2 3p6 4s2 3d6

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22
Q

What is the electron configuration of cobalt?

A

1s2 2s2 2p6 3s2 3p6 4s2 3d7

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23
Q

What is the electron configuration of nickel?

A

1s2 2s3 2p6 3s2 3p6 4s2 3d8

24
Q

What is the electron configuration of copper?

A

1s2 2s2 2p6 3s2 3p6 4s1 3d10

25
Q

What is the electron configuration of zinc?

A

1s2 2s2 2p6 3s2 3p6 4s2 3d10

26
Q

How do transition metals form ions?

A

Lose their 4s electrons before their 3d electrons, even though the 4s shell is filled first (3d and 4s orbitals are very close together + once electrons occupy the orbitals, the 4s electrons have a higher energy + are lost first

27
Q

What are the physical properties of transition elements?

A
  • metals
  • high densities
  • high melting and boiling points
  • shiny
  • when solid: giant metallic lattices containing delocalised electrons, which move freely to conduct electricity
28
Q

What are the chemical properties of transition metals?

A
  • variable oxidation states (leads to disproportionation)
  • form coloured compounds
  • good catalysts
29
Q

Describe the variable oxidation states of transition metals.

A
  • more than one stable oxidation state

- all form +2 ions (mostly from losing 4s electrons as they’re in the highest occupied energy level)

30
Q

Why are transition metals used as catalysts in industry?

A
  • reduce the amount of energy required to reach the activation energy of a reaction by reducing the activation energy to make a reaction start
  • increase profits of company
  • can reduce the time needed to make a product
31
Q

Give one drawback of transition metals being used as catalysts in industry.

A

There’s risks due to the toxicity of transition metals

32
Q

Using aluminium hexaaqua and copper tetrachloride as an example, how does the central metal ion of complex ions form coordinate bonds with numbers other ligands.

A
  • 3s, 3p and 2 3d orbitals hybridise to form an sp3d2 orbital, so Al can bond to 6 ligand molecules (think the orbitals with no electrons in hybridise)
  • produces 6 orbitals of the same energy + becomes energetically stable
  • empty 4s + 4p orbitals used in a hybridised form to accept lone pair from chloride ions
33
Q

How is the coordination number calculated?

A

the number of coordinate bonds formed with the central metal ion from ligands but NOT NECESSARILY THE SAME AS THE NUMBER OF LIGANDS THERE ARE

34
Q

Describe the distribution of charge across a complex ion like aluminium hexaaqua.

A

Charge distributed evenly over the whole molecule

35
Q

When all the ligands are chloride ions, why can you only get 4 around the central metal ion compared to the 6 water ligands you can fit around the central metal ion.

A

Chloride ions are bigger so less can fit around. Greater repulsion

36
Q

What is the structural formula for the ligand represented by en?

A

NH2CH2CH2NH2

1,2-diaminoethane

37
Q

Give 2 examples of bidentate ligands.

A
  • 1,2-diaminoethane, NH2CH2CH2NH2

- ethandioate ion, COOCOO

38
Q

Give an example of a quadridentate ligand.

A

Haemoglobin

39
Q

Describe the structure and bonding in the haemoglobin quadridentate ligand.

A
  • Fe2+ ion surrounded by haem (hollow ring of C w H atoms) at centre which are 4 N atoms w lone pairs on them
  • haem is 1 of a group of similar compounds called porphyrins (similar ring structure w different groups attached to the outside of the ring)
  • each lone pair on N atoms for coordinate bond w Fe2+ ion holding it at the centre of the complicated ring of atoms
  • Fe has 4 coordinate bonds w haem but has space to form 2 more (1 above + 1 below plane of ring)
  • the protein global attaches to 1 of these positions using a lone pair of electrons on 1 of the N’s in 1 of its amino acids
  • coordination number: 6
40
Q

Give an example if a hexadentate ligand.

A

-EDTA (4- charge)

-OOCCH2)2NCH2CH2N(CH2COO-

41
Q

What is the electron configuration of Cr+?

A

1s2 2s2 2p6 3s2 3p6 3d5

42
Q

What is the electron configuration of Mn2+?

A

1s2 2s2 2p6 3s2 3p6 3d5

43
Q

What is the electron configuration of Sc3+?

A

1s2 2s2 2p6 3s2 3p6

44
Q

What is the electron configuration of Ti3+?

A

1s2 2s2 2p6 3s2 3p6 3d1

45
Q

What is a monodentate ligand?

A

(aka unidentate) Can only form 1 coordinate bond with the central metal ion

46
Q

Give an example of a complex ion with a square planar shape.

A

Cisplatin

47
Q

Describe the structure of cisplatin and what it is used for.

A
  • [Pt(NH3)2Cl2]
  • square planar shape
  • coordination number: 4
  • interferes with DNA replication
  • binds to DNA+ stops cell division
  • so cancerous cells destroyed
  • assume platinum always makes square planar shapes fro complex ions
  • lone pair on top and bottom to give square planar shape around platinum ion
48
Q

What is a bidentate ligand?

A

Ligand donates 2 lone pairs of electrons to the central metal ion to form 2 coordinate bonds

49
Q

What is an optical isomer?

A
  • 2 enantiomers rot plane polarised light differently
  • 1 clockwise + the other anticlockwise
  • mirror images
  • non superimposable
50
Q

What is a ligand substitution reaction?

A

One in which one or more ligands in a complex ion are replaced by one another

51
Q

Describe the colour changes when chloride ions are added to hexaaquacobalt.

A 
[Co(H2O)6]2+(aq) + 4Cl-(aq) ⇌ [CoCl4]2-(aq) + 6H2O(l)
pink solution (hexaaquacobalt) to a blue solution (tetrachlorocobalt)
52
Q

Describe the colour changes as chloride ions are added to heaxaaquacopper.

A

[Cu(H2O)6]2+(aq) + 4Cl-(aq) ⇌ [CuCl4]2-(aq) + 6H2O(l)

pale blue solution ⇌ yellow solution (may appear green from yellow and blue mixing)

53
Q

What is the reaction and colour change when copper tetrachloride is added with excess ammonia?

A

Goes from a yellow solution to a dark blue solution

[CuCl4]2- —-> [Cu(NH3)4(H2O)2]2+

54
Q

In ligand substitution, where can the OH- ions come from?

A

From NaOH solution of NH3 solution as forms NH4OH

55
Q

What causes the distorted octahedral shape of [Cu(NH3)4(H2O)2]2+?

A

Cu-O are longer than the Cu-N bonds

56
Q

In the reaction between heaxaaquacopper and ammonia, why is there some blue precipitate formed?

A

Cu(OH)2 because ammonia acts as an alkali

57
Q

What kind of ligands usually need to be present in order for a complex ion to exhibit optical isomerism?

A
  • 6 different monodentate ligands
  • 2 bidentate + 2 monodentate ligands
  • 3 bidentate ligands

Chemistry (13 decks)

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