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OCR A LEVEL CHEMISTRY > 5.3.1 Transition Elemtns and 5.3.2 Qualitative Analysis > Flashcards

5.3.1 Transition Elemtns and 5.3.2 Qualitative Analysis Flashcards

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1
Q

Define a transition element

A

A d block element that forms atleast 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 the 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 mp and bp
shiny
good conductor of heat and electricity
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9
Q

What are the characteristic chemical properties of transition metals?

A

Variable oxidation states
take part in any redox reactions

Coloured compounds / ions in solution

Good catalysts

Form complex ions

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10
Q

In potassium manganate (Vll), 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)?

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 o 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 coordinate 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

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

How many coordinate bonds does EDTA 4- form?

A

6

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23
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

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24
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

25
Q

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

A

linear

26
Q

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

A

Tetrahedral

27
Q

Name as exception to the general rule that ions with 4 ligands is generally tetrahedral. What shape is it?

A

Platin is square planar

forms cisplatin

28
Q

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

A

Octahedral

29
Q

How can complex ions display EZ pr zis 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 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

30
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

31
Q

What is cis-platin used for?

Describe its mechanism of action

A

I 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

32
Q

Which metal ion is present in a haem group?

A

FE2+

33
Q

What is the coordination number of a haem group?

A

6

34
Q

What are the ligands in haem group?

A

4 nitrogen forming the porphyrin ring
1 oxygen
1 globin

35
Q

Why is CO toxic?

A

CO also coordinately bonds to the Fe 2+, and bonds more strongly to FE 2+ than O2.

Stops O2 from bonding to haemoglobin, so O2 cannot be transported around the body

36
Q

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

A

Pale blue

37
Q

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

A

Deep blue

38
Q

What colour is [ CuCl4]2- solution?

A

Yellow

39
Q

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

A

Dark green

40
Q

What is a precipitation reaction?

A

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

41
Q

What colour is Fe 2+ aqua ion?

A

Green

42
Q

What colour is Fe3+ aqua ion?

A

Pale brown

43
Q

What colour is Cr3+ aqua ion?

A

Violet

44
Q

What colour is Mn2+ aqua ion?

A

Pink

45
Q

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

A

Blue

46
Q

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

A

Green

47
Q

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

A

Brown

48
Q

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

A

Green

49
Q

When Fe 3+ reacts with NH3 or OH-, what colour is the precipitate?

A

Brown

50
Q

What colour is MnO4-

A

purple

51
Q

Write a half equation for the reduction of MnO4 - to Mn 2+

A

MnO4 - + 8 H+ + 5e- –> Mn 2+ + 4 H2O

52
Q

Why are redox titrations with transition metal compounds said to b awlf indicating?

A

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

53
Q

What colour is Cr2O7 2-?

A

Orange

54
Q

What colour is Cr3+?

A

Green

55
Q

Write a half equation for the reduction of Cr2O7 2- to Cr3+

A

Cr2O7 2- + 14 H+ + 6e- —> 2 Cr 3+ + 7H2O

56
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

57
Q

Write the method used to test fpr 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

58
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.

OCR A LEVEL CHEMISTRY (48 decks)

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