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transition metals Flashcards

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1
Q

What is the aqueous ion of copper(II) and what is its colour?

A

[Cu(H₂O)₆]²⁺(aq)

blue solution

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2
Q

What is the aqueous ion of iron(II) and what is its colour?

A

[Fe(H₂O)₆]²⁺(aq)

green solution

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3
Q

What is the aqueous ion of iron(III) and what is its colour?

A

[Fe(H₂O)₆]³⁺(aq)

yellow solution

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4
Q

What is the aqueous ion of chromium(III) and what is its colour?

A

[Cr(H₂O)₆]³⁺(aq)
purple solution

*May appear green due to other complex ions e.g. [Cr(H₂O)₅(OH)]²⁺

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5
Q

What is the aqueous ion of manganese(II) and what is its colour?

A

[Mn(H₂O)₆]²⁺(aq)

pale pink solution

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6
Q

What is the substance of copper(II) produced following its reaction with NaOH and what is the colour?

A

Cu(H₂O)₄(OH)₂

blue precipitate

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7
Q

What is the substance of iron(II) produced following its reaction with NaOH and what is the colour?

A

Fe(H₂O)₄(OH)₂
green precipitate

goes rusty brown on standing in air

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8
Q

What is the substance of iron(III) produced following its reaction with NaOH and what is the colour?

A

Fe(H₂O)₃(OH)₃

rusty brown precipitate

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9
Q

What is the substance of chromium(III) produced following its reaction with NaOH and what is the colour?

A

Cr(H₂O)₃(OH)₃

green precipitate

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10
Q

What is the substance of manganese(II) produced following its reaction with NaOH and what is the colour?

A

Mn(H₂O)₄(OH)₂
brown precipitate

which darkens on standing in air

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11
Q

Which precipitate is affected if excess NaOH is added?

A

chromium precipitate/Cr(H₂O)₃(OH)₃

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12
Q

What is the substance of chromium(III) produced following its reaction with EXCESS NaOH and what is the colour?

A

[Cr(OH)₆]³⁻(aq)

green solution

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13
Q

What is the substance of copper(II) produced following its reaction with NH₃ and what is the colour?

A

Cu(H₂O)₄(OH)₂

blue precipitate

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14
Q

What is the substance of iron(II) produced following its reaction with NH₃ and what is the colour?

A

Fe(H₂O)₄(OH)₂
green precipitate

goes rusty brown on standing in air

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15
Q

What is the substance of iron(III) produced following its reaction with NH₃ and what is the colour?

A

Fe(H₂O)₃(OH)₃

rusty brown precipitate

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16
Q

What is the substance of chromium(III) produced following its reaction with NH₃ and what is the colour?

A

Cr(H₂O)₃(OH)₃

green precipitate

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17
Q

What is the substance of manganese(III) produced following its reaction with NH₃ and what is the colour?

A

Mn(H₂O)₄(OH)₂
brown precipitate

which darkens on standing in air

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18
Q

Which precipitate is affected if excess NH3 is added?

A

chromium precipitate/Cr(H₂O)₃(OH)₃

copper precipitate/Cu(H₂O)₄(OH)₂

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19
Q

What is the substance of copper(II) produced following its reaction with EXCESS NH₃ and what is the colour?

A

[Cu(H₂O)₂(NH₃)₄]²⁺(aq)

deep blue solution

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20
Q

What is the substance of chromium(III) produced following its reaction with EXCESS NH₃ and what is the colour?

A

[Cr(NH₃)₆]³+(aq)

purple solution

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21
Q

What is the substance of copper(II) produced following its reaction with HCl and what is the colour?

A

[CuCl₄]²⁻(aq)

yellow solution

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22
Q

What is the substance of _____ produced following its reaction with HCl?

  • iron(II)
  • iron(III)
  • chromium(III)
  • manganese(II)

*For these you don’t need to know the colour, just the ion ormed and type of substance (solution/precipitate)

A
  • [FeCl₄]²⁻(aq)
  • [FeCl₄]⁻(aq)
  • [CrCl₄]⁻(aq)
  • [MnCl₄]²⁻(aq)
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23
Q

What colour solution is Cr₂O₇²⁻(aq)?

A

orange solution

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24
Q

How are Cr₂O₇²⁻(aq) ions made?

A
  • from oxidation of Cr³⁺ using H₂O₂/OH-
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25
Q

How can Cr₂O₇²⁻(aq) ions be reduced back to Cr³⁺?

A
  • reduced back to Cr³⁺ using Zn/H+
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26
Q

How are CrO₄²⁻(aq) ions made?

A
  • from oxidation of Cr³⁺ using H₂O₂/OH-
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27
Q

What colour solution is CrO₄²⁻(aq)?

A

yellow solution

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28
Q

What colour solution solution is Cr²⁺(aq)?

A

blue solution

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29
Q

How are Cr²⁺(aq) ions made?

A

reduction of Cr³⁺ using Zn

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30
Q

What colour solution are MnO₄²⁻(aq)?

A

purple solution

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31
Q

How are MnO₄²⁻(aq) ions made?

A

Made by oxidation of Mn²⁺

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32
Q

What is the colour of the precipitate Mn₂O₃(s)?

A

Dark brown precipitate

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33
Q

How is Mn₂O₃(s) made?

A

Made by oxidation of Mn(OH)₂ by oxygen

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34
Q

You don’t need to know this however it may be useful:

A
  • Cu⁺ = colourless solution
  • Zn²⁺/Sc³⁺ = colourless solution (not transition metals)
  • Zn(H₂O)₄(OH)₂/Sc(H₂O)₃(OH)₃ = white precipitate
  • CuI = white solid (formed by reduction of Cu²⁺ using I⁻
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35
Q

Define transition metal.

A

A transition metal is a d-block element that has an incomplete d sub-shell as a stable ion.

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36
Q

What is a d-block element?

A

A d-block element is an an element in which the highest energy level electrons are found in a d sub-shell.

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37
Q

Which two metals in the d-block elements are not transition elements?

A

Zinc and Scandium

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38
Q

Why is zinc not a transition metal?

A

Zinc forms only the Zn2+ ion, in which the d-orbitals are full.

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39
Q

Why is scandium not a transition metal?

A

Scandium orms only the Sc3+ ion, in which the d-orbitals are empty.

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40
Q

We know how electrons fill the orbitals of a sub-shell however two transition elements do not fil in this order. Which ones?

A

Chromium and copper

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41
Q

What is the electronic configuration of chromium atoms?

A

1s²2s²2p⁶3s²3p⁶4s¹3d⁵

As you can see, 3d started to fill without all of 4s filling up.

42
Q

What is the electronic configuration of copper atoms?

A

1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰

As you can see, 3d started to fill without all of 4s filling up.

43
Q

Why does chromium and copper atoms fill up differently to the other transition metals?

A

This is becaause in these two elements, the electrons repulsions between the outer electrons are minimised, resulting in an increased stability of the chromium and copper atoms.

44
Q

Physical properties of transition metals?

A
  • High melting and boiling point
  • High densities
  • Hard
45
Q

Chemical properties of transition metals?

A
  • Stable in multiple oxidation states
  • Form coloured compounds
  • Acts as catalysts in chemical reactions
46
Q

When is a transition metal in its highest oxidation state?

A

The highest oxidation state of a transition metal is often found in a strong oxidising agent.
E.g. KMnO₄, a strong oxidising agent, where manganese is in its highest oxidation state, +7

47
Q

What is disproportionation reaction?

A

Where one specie is both reduced and oxidised.

48
Q

Transition metals act as catalysts. What are the two main ways in which catalysis takes places?

A
  • Transition metals provide a surface on which a reaction can occur. Reactants are adsorbed onto the surface of the metal and held in palces while the reaction occurs. Ater reaction occurs, products desorbed and metal remains unchanged.
  • Transition metal ions have the ability to change their oxidation states by gaining or losing electrons. They then bind to reactants forming intermediates as part of a chemical pathway, often with a lower activation energy, which speeds up the reaction.
49
Q

Why are transition metal catalysts used in industry?

A

increases rate of reaction + reduces energy required for reaction - so lower temperatures can be used = more profitable for the industrial process

*Transiton metal compounds can however be toxic so handle with care

50
Q

When does a transition metal catalyst need to be disposed?

A

When substances bind and remain in the active sites of transition metals, they stop working so have to be disposed of.

51
Q

Which process uses an iron catalyst?

A

The Haber process (production of ammonia): N₂(g) + 3H₂(g) –> 2NH₃(g)

52
Q

Which process uses a vanadium(V) oxide VO, catalysts?

A

The Contact process (conversion of sulur dioxide into sulfur trioxide which is used to manufacture sulfuric acid): 2SO₂(g) + O₂(g) –> 2SO₃(g)

53
Q

Uses of sulfuric acid?

A

involved in the production of fertilisers, detergents, adhesives + explosives.

54
Q

Which transition metal catalyst is used in the hydrogenation of alkenes?

A

Nickel

55
Q

What transition metal catalyst is used in the decomposition of hydrogen peroxide?

A

Hydrogen peroxide decomposes at RTP but a Mangaese oxide, MnO, catalyst is used to increase reaction rate. This reaction is used for the produce oxygen gas.
2H₂O₂(aq) –> 2H₂O(l) + O₂(g)

56
Q

What is the reaction to produce hydrogen gas and what is the catalyst involved?

A

Hydrogen is produced rom the reaction between zinc and sulfuric acid. Copper sulfate, CuSO₄, catalyst can be added to increase rate.
Zn(s) + H₂SO(aq) –> ZnSO₄(aq) + H₂(g)

57
Q

Define complex ion

A

A complex ion is a transition metal ion bonded to one or more ligands by coordinate bonds.
*When a transition metal is in solution it forms complex ions e.g. [Cu(H₂O)₆]²⁺(aq)

58
Q

Define ligand

A

A molecule or ion that can donate a pair of electrons to the transition metal ion to orm a coordinate bond.

59
Q

Define coordination number

A

The total number of corrdinate bonds ormed betweeen a central metal ion and its ligands.

60
Q

When writing the aqueous (complex) ion of a transition metal, how do you calculate the overall charge outside the square brackets?

*square brackets group together the species making up the complex ion

A

The overall charge is the sum of the individual charges of the transition metal ion and ligands.

61
Q

SO…. what do all ligands have?

A

At least one lone pair of electrons in their outer energy level - some neutral, some charged.

62
Q

What is a monodentate ligand?

A

A monodentate ligand is a ligand that donates just one pair of electrons to the central metal ion to form one coordinate bonds
- Baso: A ligand that forms one coordinate bond.

63
Q 
State the charge on these monodentate ligands:
\:OH₂
\:NH₃
\:SCN-
\:CN-
\:Cl-
\:OH-
A 
Neutral
Neutral
-1
-1
-1
-1
64
Q

What are bidentate ligands?

A

A bidentate ligand is a ligand that donates two pair of electrons from different atoms on the same ligand to the central metal ion to form two coordinate bonds

65
Q

Examples of bidentate ligands? Draw them.

A 
ethane-1,2-diamine (NH₂CH₂CH₂NH₂) - written as 'en' in the formula of a complex ion.
ethanedioate ion (C₂O₄²⁻)
66
Q

What is a multidentate ligand?

A

A ligand that can donate two or more pairs of electrons from different atoms on the same ligand to the central metal ion to form two or more coordinate bonds.

Hexadentate ligand is an example o a multidentate ligand that can form 6 coordinate bonds.

67
Q

Hexadentate ligand is an example o a multidentate ligand. Howe many ligands can it form?

A

6

68
Q

Give me an example of a hexadentate ligand? Draw it.

A

EDTA⁴⁻

69
Q

What is the shape and bond angle of a complex ion with 6 coordinate bonds?

A

octahedral - 90 degrees

70
Q

What is the shape and bond angle of a complex ion with 4 coordinate bonds?

A

Tetrahedral - 109.5 degrees

square planar - if the central transition metal ion is paladium or platinum

71
Q

In the complex ion [CuCl₄]²⁻, why do only 4 coordinate bonds form, because usually 6 form?

A

This is because chlroide ions are too large for 6.

72
Q

On a 3D drawing of a complex ion, what does a solid wedge hatched wedge and solid line represent?

A
  • Solid wedge - bonds come out of the plane of the paper towards you.
  • Hatched wedge, bonds go into the plane of the paper away from you.
  • Solid line - bonds in the plane of the paper.
73
Q

What is a stereoisomer?

A

Species with the same structural formula but a different arrangement o atoms in space.

74
Q

What are the two types of stereoisomerism?

A
  • cis-trans isomersism

- optical isomerism

75
Q

In six-coordinate complexes, what requirements must be fulfilled for cis-trans isomerism to occur?

A
  • four monodentate ligands and two different monodentate ligands
  • two bidentate ligands and two monodentate ligands
76
Q

When does a cis-isomer form?

A

If the two monodentate ligands that are different to the remaining ligands are next to each other then a cis-isomer forms.

77
Q

When does a trans-isomer forms?

A

When the two different monodentate ligands opposite to each other.

78
Q

For a four-coordinate complex, cis-trans isomerism is just like organic chemistry so, how does a cis-isomer and trans-isomer form?

A

Cis: the same two ligands adjacent to each other
trans: the same two ligands opposite each other

79
Q

What is cis-platin? Draw it.

A

A cis-isomer of a platimun complex, [PtCl₂(NH₃)₂]

80
Q

What is the application of cis-platin?

A

Cis-platin is a drug to treat cancer (chemotherapy). It binds to the DNA of fast-growing cells e.g. cancer cells, to prevent these cells from dividing. Activation of the cell’s own repair mechanism leads to death of the cell.

81
Q

Which drug has replaced cis-platin recently and why?

A

carboplatin as it has fewer side afects and requires lower doses

82
Q

Optical isomerism usually occurs with octahedral complex. What requirements must be filled for optical isomerism in a octahedral complex ?

A
  • complex with three bidentate ligands
  • complex with two bidentate ligands and two monodentate ligands
  • complex with a hexadentate ligand.
  • to draw optical isomer just draw mirror line then copy.
83
Q

How to distinguish between optical isomers?

A

Optical isomers rotate plane polarised light differently - one of the isomers rotate light clockwise and the other rotates anticlockwise.

84
Q

What is ligand substitution?

A

This is when one ligand in a complex is replaced by another ligand.

85
Q

If the ligand sizes of the current ligand and the one to be substituted is similar, what happens to the coordination number and shape?

A

Coordination number and shape of complex ion remains the same.

86
Q

If the ligand sizes of the current ligand and the one to be substituted is not similar, what happens to the coordination number and shape?

A

Coordination number and shape of complex ion remains the same.

87
Q

Give an example of a reaction where ligand substitution does not change the coordination number and shape of molecule?

A

reaction of aqueous chromium(II) with excess ammonia:

[Cr(H₂O)₆]³⁺(aq) + 6NH₃(aq) –> [Cr(NH₃)₆]³⁻(aq) + 6H₂O(l)

88
Q

Give an example of a reaction where ligand substitution does change the coordination number and shape of molecule?

A

reaction of aqueous copper(II) ions with hydrochloric acid:[Cu(H₂O)₆]²⁺(aq) + 4Cl-(aq) –> [CuCl₄]²⁻(aq) + 6H₂O(l)

89
Q

Partial ligand substitution can also occur. Give me an example of a reaction where partial ligand substitution occurs?

A

reaction of aqeous copper(II) ions and excessammonia: [Cu(H₂O)₆]²⁺(aq) + 4NH₃(aq) –> [Cu(H₂O)₂(NH₃)₄]²⁺(aq) + 4H₂O(l)

90
Q

Explain how ligand substituion allows haemoglobin to transport oxygen in the blood?

A

Blood contains haemoglobin. Each haemoglobin contains haem groups which has an Fe²⁺ ion at the centre, where an oxygen molecule can bind to REVERSIBLY through the formation of a coordinate bond (in order to join and be released).

91
Q

In the presence of carbon monoxide, less oxygen is carried in the blood. Suggest why?

A

This is because the carbon moxide binds irreversibly to the Fe²⁺ in the haem group (forming a coordinate bond). The carbon monoxide can also substitute/replace an already bonded oxygen too. This may lead to headaches nausea, and even death.

92
Q

Describe CO?

A

odourless, colourless, toxic gas, prodcued in incompletely combustion of fuels.

93
Q

What is a precipitation reaction?

A

A precipitation reaction is one in which sluble ions, in seperate solutions, are mixed together to produce an insoluble compound known as a precipitate.

94
Q

We have already looked at the colours p the starting solution and formed precipitate in a precipitate reaction but how do you write the ionic equations for NaOH with:
Cu²⁺(aq), Fe²⁺(aq) and Cr³⁺(aq)?

A

[Cu(H₂O)₆]²⁺(aq) + 2OH- –> Cu(H₂O)₄(OH)₂ + 2H₂O(l)

[Fe(H₂O)₆]²⁺(aq) + 2OH- –> Fe(H₂O)₄(OH)₂ + 2H₂O(l)

[Fe(H₂O)₆]³⁺(aq) + 3OH- –> Fe(H₂O)₃(OH)₃ + 3H₂O(l)

*Can also be written like Cu²⁺(aq) + 2OH-(aq) –> Cu(OH)₂(s)/Fe²⁺(aq) + 2OH-(aq) –> Fe(OH)₂(s)

95
Q

How to test for the ammonium ion, NH₄⁺?

A

add NaOH(aq). If distinctive smelling gas produced turns red litmus paper blue, sample contained ammonium ions.

96
Q

How to test for carbonate ion, CO₃²⁻?

A

Add strong acid e.g. HCl. Collect gas produced and bubble through limewater. Limewater goes cloudy from colourless if you started with carbonate ions.

97
Q

How to test for sulfate ion, SO₄²⁻

A
  • Add dilute HCl, then barium chloride. If white precipitate of barium sulfate produced, sample contained sulfate ions.
98
Q

How to test for halide ions?

A

Dissolve suspected halide in water. Add dilute nitric acid and an aqueous solution of silver nitrate.
White precipitate of AgCl = sample contained Cl- ions
Cream precipitate of AgBr = Br- ions
Yellow precipitate of AgI = I- ions

99
Q

If coulour of halide precipitates cannot be distinguihsed what can we do?

A

Add dilute ammonia then conc. ammonia:
AgCl soluble in dilute ammonia and concentrated ammonia
AgBr soluble in concentrated ammonia only
AgI insoluble in both dilute and concentrated ammonia.

100
Q

What order should negative ions/cations be tested?

A

Carbonate –> sulfate –> halide
Because bariums ions can react with carbonate ions to produce white precipitate of BaCO₃. Silver ions form a white precipitate of Ag₂SO₄

Chemistry OCR AS Level (9 decks)

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