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OFFICIAL OCR A-Level Chemistry > Chapter 24 - Transition Elements > Flashcards

Chapter 24 - Transition Elements Flashcards

D-block element, The formation and shapes of complex ions, Stereoisomerism in complex ions, Ligand substitution and precipitation, Redox and qualitative analysis.

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1
Q

What are the two irregularities in the d-block in terms of electron configuration?

A

Chromium: 3d5 4s1 instead of 3d4 4s2
Copper: 3d10 4s1 instead of 3d9 4s2

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2
Q

Why do these irregularities exist in the d block electron configurations?

A

A half filled and a fully filled d sub shell gives greater stability to these atoms.

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3
Q

What are transition elements?

A

D-block elements that form at least one ion with a partially filled d-orbital.

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4
Q

Which d-block elements are excluded from being transition elements?

A

Scandium(Sc3+) and zinc(Zn2+)

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5
Q

What are the properties of the transition elements?

A

Form compounds in which the transition element has different oxidation states
Form coloured compounds
Elements and compounds can act as catalysts

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6
Q

What colours are the various ions of Chromium?

A

+3 green

+6 orange

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7
Q

What colours are the various ions of Copper?

A

+2 blue

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8
Q

What colour is potassium dichromate(VI)?

A

Orange

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9
Q

What colour is cobalt(II) chloride?

A

Blue

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10
Q

What colour is nickel(II) sulfate?

A

Green

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11
Q

What colour is hydrated copper(II) sulfate?

A

Blue

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12
Q

What is the catalyst used in the Haber process?

A

Iron

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13
Q

What is the catalyst used in the Contact process?

A

Vanadium(V) oxide

V2O5

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14
Q

What is the catalyst used in hydrogenation?

A

Nickel

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15
Q

What is the catalyst used in catalytic decomposition of hydrogen peroxide?

A

Manganese(IV) oxide

MnO2

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16
Q

Define what a complex ion is

A

A transition metal ion bonded to ligands by coordinate bonds.

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17
Q

Define coordination number

A

The number of coordinate bonds attached to the central metal ion.

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18
Q

Define what a ligand is

A

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

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19
Q

What is meant by a monodentate ligand?

A

A ligand that is able to donate one pair of electrons to a central metal ion.

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20
Q

Give 6 examples of common monodentate ligands and their charges

A 
Water H2O neutral
Ammonia NH3 neutral
Thiocyanate SCN- -1
Cyanide CN- -1
Chloride Cl- -1
Hydroxide OH- -1
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21
Q

What shape is created from a complex ion having a coordination number of 6?

A

Octahedral

22
Q

What shapes can be created from a complex ion having a coordination number of 4?

A

Tetrahedral
OR
Square planar

23
Q

When is a square planar shape formed in a complex ion?

A

When the transition metal in the complex ion has eight d-electrons in the highest energy d-sub-shell.

24
Q

What is stereoisomerism?

A

Same structural formula but a different arrangement of the atoms in space.

25
Q

What are the two types of stereoisomerism?

A

Cis-trans isomerism

Optical isomerism

26
Q

When can complex ions show cis-trans isomerism?

A

Four or six coordinate complex ions with two different monodentate ligands.

27
Q

When can complex ions show both types of stereoisomerism?

A

Six coordinate complex ions containing monodentate and bidentate ligands.

28
Q

What is optical isomerism?

A

Non-superimposable mirror images of each other.

Called enantiomers

29
Q

Define ligand substitution

A

One ligand in a complex ion is replaced by another ligand.

30
Q

Describe ligand substitution of aqueous copper(II) ions with ammonia

A

Four of the waters are replaced by ammonia ligands, the solution turns from pale blue to dark blue.

31
Q

Describe ligand substitution of aqueous copper(II) ions with chloride ions

A

The six water ligands are replaced by four chloride ion ligands. The solution starts out pale blue and moves to yellow on completion.

32
Q

Why does the solution of aqueous copper (II) ions reacting with chloride ions turn green as the reaction proceeds?

A

The yellow and blue solutions mixing gives a green colour.

33
Q

Why does the shape of the aqueous copper (II) ion change from octahedral to tetrahedral when it reacts with chloride ions?

A

Chloride ligands are larger in size than water ligands so fewer of them can fit around the Cu2+ ion.

34
Q

What is formed when chromium(III) potassium sulphate is dissolved in water?

A

The complex ion [Cr(H2O)6]3+ is formed.

A pale purple solution.

35
Q

What is formed instead when only chromium(III) sulphate is dissolved in water?

A

The complex ion [Cr(H2O)5SO4]+ is formed.

A green solution.

36
Q

Describe the reaction between [Cr(H2O)6]3+ and an excess of aqueous ammonia

A

A grey green precipitate of Cr(OH)3 is formed initially.
Cr(OH)3 dissolves in excess ammonia to form the complex ion [Cr(NH3)6]3+.
A purple solution.

37
Q

How does ligand substitution help with gas exchange in blood?

A

In haemoglobins there is a central Fe2+ ion that can bind to oxygen gas.
The oxygen is released to cells and carbon dioxide can bond to the Fe2+ where it is released in the lungs.

38
Q

What is a precipitation reaction?

A

Two aqueous solutions containg ions react together to form an insoluble ionic solid.

39
Q

Describe the precipitation reaction of Cu2+ with NaOH

A

Blue solution reacts to form a blue precipitate of copper(II) hydroxide.
Insoluble in excess NaOH.

40
Q

How do Fe2+, Fe3+ and Mn2+ react with an excess of aqueous ammonia?

A

Same way as they react with NaOH.
Form hydroxide precipitates.
Insoluble in excess ammonia.

41
Q

uses of silver, nickel l, zinc

A

jewellery, coins

42
Q

uses of iron

A

steel also as a catalyst in the harbor process

43
Q

Uses of copper

A

wires, pipes

44
Q

Uses of titanium

A

uses in aerospace industry due to high strength, joint replacement and cosmetic dentistry

45
Q

No charge on complex makes it

A

It makes it insoluble in solution

46
Q

What is the colour of Manganese ion?

A

Mn2+ is Pale Pink

47
Q

What are the various colours of Iron ions?

A

Fe2+ is Pale Green

Fe3+ is Yellow

48
Q

Why are the results the same when you add ammonia and when you add NaOH to transition metal?
Explain with aid of eqn

A

NH3 + H20 –> NH4+ + OH-

  • Ammonia in aq solution
  • OH- is present
49
Q

What colour is Co2+?

A

Pink

50
Q

What colour is aqueous Cr3+?

A

Violet

OFFICIAL OCR A-Level Chemistry (35 decks)

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