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A Level Chemistry OCR A > 5.3.1: Transition elements and 5.3.2: Qualitative analysis > Flashcards

5.3.1: Transition elements and 5.3.2: Qualitative analysis Flashcards

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1
Q

Define a transition element

A

A d block element that forms at least one stable ion with partially filled d subshell

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2
Q

Where are the transition metals located in the

periodic table?

A

In the middle block from Ti to Cu

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3
Q

What are the 2 elements in d block that are not

considered as transition metals?

A

Scandium and zinc

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4
Q

Why is scandium and zinc not considered as

transition metals?

A

Scandium only forms Sc3+, where the d orbitals are empty

Zinc only forms Zn2+ where the d orbitals are full

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5
Q

What is the noble gas configuration of chromium?

A

[Ar]4s1 3d5

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6
Q

What is the noble gas configuration of copper?

A

[Ar]4s1 3d10

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7
Q

Which electrons do transition metals lose first when

forming ions?

A

4s

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8
Q

What are some characteristic physical properties of

transition metals?

A 
● Metallic
● High density
● High melting and boiling point
● Shiny
● Good conductors of heat and electricity
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9
Q 
What are the characteristic chemical properties of
transition metals (4 marks)?
A

● Variable oxidation states → take part in many redox reactions
● Coloured compounds/ions in solution
● Good catalysts
● Form complex ions

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10
Q

In potassium manganate (VII), what is the oxidation

number of Mn?

A

Mn = +7

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11
Q

What are the 2 main ways in which transition metals act

as an effective catalyst?

A

● They provide a surface on which reaction can take place
● They change oxidation states to form
intermediates required for pathways with lower
activation energy

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12
Q

Give some examples of transition metal catalysts and the

processes/reactions they catalyse (4 marks)?

A 
● Iron - Haber process
● Vanadium (V) oxide - contact process
● Nickel - hydrogenation of alkenes
● Manganese (IV) oxide - decomposition of hydrogen
peroxide
● Copper sulfate - hydrogen production
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13
Q

What is a complex ion?

A

Transition metal ion bonded to one or more ligands by coordinate bonds

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14
Q

Define a ligand

A

Molecule or an ion that can donate a pair of electrons to the metal to form a coordinate bond

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15
Q

What is a coordinate bond?

A

A bond in which one of the atom provides both the electrons required for bonding, also known as dative bonding.

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16
Q

What does the coordination number indicate?

A

The number of coordinate bonds formed

between the metal ion and its ligands

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17
Q

What is a mono/unidentate ligand?

A

A ligand that forms one co-ordinate bond to the central metal ion (one lone pair to donate)

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18
Q

What is a bidentate ligand?

A

A ligand that forms two coordinate bonds
to the central metal ion (2 lone pairs to
donate)

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19
Q

What is a multidentate ligand?

A

A ligand that forms three or more

coordinate bonds to the central metal ion

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20
Q

Give some examples of common monodentate

ligands (4 marks).

A

Cl-, H2O, NH3, CN

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21
Q

Name the most common bidentate ligand

A

ethane-1,2-diamine

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22
Q

ethanedioate; how many coordinate bonds can

it form to a transition metal ion?

A

2 co-ordinate bonds

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23
Q

benzene-1,2-diol; how many coordinate bonds

can it form to a transition metal ion?

A

2 coordinate bonds

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24
Q

ethane-1,2-diamine. What is its shortened

name? How many coordinate bonds does it form?

A

2 coordinate bonds, shortened name = en

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25
Q

How many coordinate bonds does EDTA4- form?

A

six

26
Q

EDTA is a chelating agent, what does that mean?

A

EDTA decreases the concentration of
metal ions in the solution by binding to
them and forming complex ions

27
Q

What ion is usually formed when a transition metal compound is dissolved in water? What shape is it?

A

Aqua ion, 6 H2O ligands around the central metal ion. Octahedral complex ion is formed

28
Q

If a transition metal ion has 2 ligands, what shape is

it usually?

A

Linear

29
Q

If a transition metal ion has 4 ligands, what shape is

it usually?

A

Tetrahedral

30
Q

Name an exception to the general rule that ions with

4 ligands is generally tetrahedral. What shape is it?

A

Platin is square planar → forms cisplatin

31
Q

What shape is a complex ion if it has 6 ligands?

A

Octahedral

32
Q

How can complex ions display E-Z or cis-trans

isomerism? What shapes of ions does this apply to?

A

Ligands differ in the way in which they are arranged in space
2 ligands of the same type can be on the same side of the metal ion (next to each other), which forms the E or cis isomer
2 ligands of the same type can be on opposite sides of the metal ion (not next to each other), which forms the Z or trans isomer
Applies to square planar and octahedral complex ions

33
Q

What conditions are needed for a complex ion to

display optical isomerism?

A

Usually applies to octahedral molecules with 2 or more bidentate ligands, so that the mirror images are non-superimposable

34
Q

What is cis-platin used for? Describe its mechanism

of action

A

It is used as an anti-cancer drug

It binds to DNA of fast growing cancer cells and prevents cell division, hence reducing the growth of cancer

35
Q

Which metal ion is present in a haem group?

A

Fe2+

36
Q

What is the coordination number of a haem group?

A

6

37
Q

What are the ligands in haem group?

A

4 nitrogen forming the porphyrin ring
1 oxygen
1 globin

38
Q

Why is CO toxic?

A

CO also coordinately bonds to the Fe2+,and bonds more strongly to Fe2+ than O2.
Stops O2 from bonding to haemoglobin, so O2 cannot be transported around the body

39
Q

What colour is [Cu(H2O)6]2+ solution?

A

pale blue

40
Q

What colour is [Cu(NH3)4(H2O)2]2+ solution?

A

deep blue

41
Q

What colour is [CuCl4]2- solution?

A

yellow

42
Q

What colour is [Cr(H2O)6]3+ solution?

A

dark green

43
Q

What is a precipitation reaction?

A

A reaction where soluble ions in separate solutions are mixed to form an insoluble compound

44
Q

What colour is Fe2+’s aqua ion?

A

green

45
Q

What colour is Fe3+’s aqua ion?

A

pale brown

46
Q

What colour is Cr3+’s aqua ion?

A

violet

47
Q

What colour is Mn2+’s aqua ion?

A

pink

48
Q

When Cu2+ reacts with NH3 or OH-, what colour is the precipitate?

A

blue

49
Q

When Fe2+ reacts with NH3 or OH-, what colour is the

precipitate?

A

green

50
Q

When Mn2+ reacts with NH3 or OH-, what colour is the precipitate?

A

brown

51
Q

When Cr3+ reacts with NH3 or OH-, what colour is the

precipitate?

A

green

52
Q

When Fe3+ reacts with NH3 or OH-, what colour is the

precipitate?

A

brown

53
Q

What colour is MnO4-?

A

purple

54
Q

Write a half equation for the reduction of MnO4- to

Mn2+

A

MnO4- + 8H+ + 5e- → Mn2+ + 4H2O

55
Q

Why are redox titrations with transition metal

compounds said to be self-indicating?

A

They usually involve a colour change as
the metal is changing oxidation state;
sometimes an indicator is still
needed/useful

56
Q

What colour is Cr2O72-?

A

orange

57
Q

What colour is Cr3+?

A

green

58
Q

Write a half equation for the reduction of Cr2O72- to Cr3+.

A

CrO72- + 14H+ + 6e- → 2Cr3+ + 7H2O

59
Q

Describe how to test for metal ions

A

● Fill half of the test tube with the sample
● Add aqueous ammonia or sodium
hydroxide drop by drop
● Colour of precipitate indicates the ion present

60
Q

Write the method used to test for ammonium ions

A

● Fill half the test tube with sample
● Add sodium hydroxide and warm gently
● Smelly gas is produced; damp red litmus paper turns blue

61
Q

Why does lime water turn milky in the presence of

carbon dioxide?

A

When carbon dioxide is bubbled in calcium hydroxide (lime water), calcium carbonate precipitate is formed

A Level Chemistry OCR A (38 decks)

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