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A-Level Chemistry > Chapter 24 Complex Ions And Ligands > Flashcards

Chapter 24 Complex Ions And Ligands Flashcards

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1
Q

What is the electron configuration for chromium?

A

3d5 4s1

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2
Q

What is the electron configuration for copper?

A

3d10 4s1

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3
Q

What is the explanation for the electron of chromium an copper being different?

A

Stability

A half-filled and fully-filled d sub-shell give additional stability to atoms of chromium and copper

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4
Q

What is lost before a 3d electron?

A

4s electron

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5
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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6
Q

What are scandium and zinc not classified as transition elements?

A

Zn2+ has a fully-filled d-orbital

Sc3+ have empty d-orbitals

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7
Q

What is a catalyst?

A

A substance that increases the rate of a reaction without itself changing

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8
Q

What are TWO examples of transition metals and their compounds being used in industry to catalyse reactions?

A

Hager process
N2 +3H2 2NH3
IRON CATALYST

Contact process
2SO2 +O2 2SO3
VANADIUM OXIDE CATALYST (V2O5)

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9
Q

What is a homogenous catalyst?

A

A catalyst that is in the same state as its reactants

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10
Q

What is a heterogenous catalyst?

A

A catalyst that is in a different state to its reactants

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11
Q

Are complex ions restricted to d-block elements?

A

No

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12
Q

What is a complex ion?

A

One or more molecules / negatively charged ions bonded to a central metal ion

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13
Q

What is ligand?

A

A molecule or ion that donates. a pair of electrons to a central metal ion to form a COORDINATE BOND or DATIVE COVALENT BOND

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14
Q

What is a dative covalent bond / coordinate bond?

A

A special kind of covalent bond where one of the bonded atoms provide both of the electrons for the shared pair

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15
Q

What is coordination number?

A

Indicates the number of coordinate bonds attached to the central metal ion

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16
Q

Which monodentate ligand seems are neutral?

A

Water and ammonia (NH3)

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17
Q

What is the difference between a monodentate ligand and a bidentate ligand?

A

Monodentate ligand donates ONE electron pair to form ONE coordinate bond

Bidentate ligand donate TWO electron pairs to form TWO coordinate bonds

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18
Q

What are examples of two common bidentate ligands?

A

1,2-

Ethanedioate ion (oxalate ion)

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19
Q

What shape do six-coordinate complexes have?

A

Octahedral shape 90

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20
Q

What shape does four-coordinate complexes have?

A

Tetrahedral 109.5 and square planar 90

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21
Q

What are some complex ions for tetrahedral shapes?

A

Co and Cu

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22
Q

Where does a square planar shape occur?

A

A square planar shape occurs in complex ions of transition metals with 8 d-electrons in the highest energy d-sub-shell

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23
Q

Which metal ions fall into the square planar shape category?

A

Platinum 2

Palladium 2

Gold 3

24
Q

What is the most common complex?

A

Six-coordinate complexes (forming octahedral shapes)

25
Q

What are the colours of the two cis-trans isomers of [Co(NH3)4Cl2]+?

A

Cis violet

Trans green

26
Q

What is another name for an optical isomer?

A

Enantiomer

27
Q

What are optical isomers?

A

Non-superimposable mirror images of each other

28
Q

What is a ligand substitution reaction?

A

Reaction in which one ligand in a complex ion is replaced by another ligand

29
Q

What is the COMPLEX and COLOUR formed when copper sulfate dissolves in water?

A

PALE BLUE

[Cu(H2O)6]2+

30
Q

What happens when an EXCESS of AMMONIA is added to a solution containing [Cu(H2O)6]2+?

A

PALE BLUE -> DARK BLUE

[Cu(H2O)6]2+ + 4NH3 -> [Cu(NH3)4(H2O)2]2+ + 4H2O

31
Q

What are the SEPARATE steps involved in the reaction of EXCESS AMMONIA with [Cu(H2O)6]2+?

A

PALE BLUE SOLUTION -> PALE BLUE PRECIPITATE of Cu(OH)2

CU(OH2) precipitation then DISSOLVES in EXCESS AMMONIA to form a a DARK BLUE solution

32
Q

What happens when EXCESS CONCENTRATED HCl is added to a solution of [Cu(H2O)6]2+?

A

PALE BLUE SOLUTION -> YELLOW SOLUTION -> BLUE SOLUTION with addition of WATER

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

33
Q

What happens when water is added to the yellow solution of [CuCl4]2-?

A

BLUE SOLUTION forms that is paler and more dilue

34
Q

Why does an intermediate green solution form when excess concentrated HCl reacts with [Cu(H2O)6]2+?

A

It is a result of yellow solution mixing with blue solution as reaction proceeds

35
Q

Why does the COORDINATION NUMBER of the COPPER complex ion change when excess concentrated HCl is added?

A

Chloride ions are larger than H2O ions so less can fit around central Cu2+ ion

Results in change in coordination number and shape from OCTAHEDRAL to TETRAHEDRAL

36
Q

What is the formula of chromium (III) potassium sulfate?

A

KCr(SO4)2.12(H2O)

37
Q

What is chromium (III) potassium sulfate also known as?

A

Chrome alum

38
Q

Which complex ion is formed when CHROMIUM (III) POTASSIUM SULFATE is dissolved in water?

A

[Cr(H2O)6]3+

VIOLET SOLUTION

39
Q

Which complex ion is formed when CHROMIUM SULFATE is dissolved in water?

A

[Cr(H2O)5SO4]+

GREEN SOLUTION

40
Q

What do both green and violet solutions of chromium contain?

A

Chromium (III) in +3 oxidation state

41
Q

What are the properties of transition metals and their compounds?

A

Form compounds in which transition metal has different OXIDATION STATES

Form COLOURED compounds

Elements and their compounds can act as CATALYSTS

42
Q

What happens (in spectate steps) when aqueous AMMONIA is added DROP-WISE to a a solution containing [Cr(H2O)6]3+?

A

Cr(OH)3 formed
VIOLET -> GREY-GREEN PRECIPITATE

Cr(OH)3 precipitate DISSOLVES in EXCESS AMMONIA to form complex ion
[Cr(NH3)6]3+
PURPLE SOLUTION

43
Q

How is blood carried around the body?

A

Presence of haemoglobin, iron-containing protein present in all blood cells

44
Q

What is the structure of haemoglobin?

A

FOUR protein chains held together by weak intermolecular forces

EACH protein chain has a HAEM molecule within its structure

Central metal ion in haem group is Fe2+ which can bind to oxygen gas

45
Q

What is the complex formed when carbon monoxide bonds to the Fe2+ ion in haemoglobin?

A

CO bonds to haemoglobin MORE STRONGLY than O2 in IRREVERSIBLE REACTION

Too high concentrations of carboxyhamepglbin can lead to death

46
Q

What is a PRECIPITATION REACTION?

A

Two aqueous solutions containing ions react together to form an insoluble ionic solid, called a precipitate

47
Q

How does Cu2+ + NaOH react?

A

Cu2+ + 2OH- -> Cu(OH)2

BLUE SOLUTION -> BLUE PRECIPITATE

INSOLUBLE IN EXCESS SODIUM NaOH

48
Q

How does Fe2+ + NaOH react?

A

Fe2+ + 2OH- -> Fe(OH)2

PALE GREEN SOLUTION -> GREEN PRECIPITATE

INSOLUBLE IN EXCESS NaOH

In air:
Turns BROWN at its SURFACE on standing in air as iron (II) is OXIDISED to iron (III)

Fe(OH)2 -> Fe(OH3)

GREEN PRECIPITATE -> ORANGE-BROWN PRECIPITATE

49
Q

How does Fe3+ + NaOH react?

A

Fe3+ + 3OH- -> Fe(OH)3

PALE YELLOW SOLUTION -> ORANGE-BROWN PRECIPITATE

INSOLUBLE IN EXCESS NaOH

50
Q

How does Mn2+ + NaOH react?

A

Mn2+ + 2OH- -> Mn(OH)2

PALE PINK SOLUTION -> LIGHT BROWN PRECIPITATE

Precipitate darkens on standing in air

INSOLUBLE IN EXCESS NaOH

51
Q

How does Cr3+ + NaOH react?

A

Fe3+ +3OH- —> Cr(OH)3

VIOLET SOLUTION —> GREY-GREEN PRECIPITATE

Soluble in excess NaOH

Cr(OH)3 + 3OH- —> [Cr(OH)6)]3-

Grey-green precipitate —> Dark green solution

52
Q

Which precipitates of which TWO central metal ions DO dissolve in excess ammonia?

A

Cu2+ and Cr2+

53
Q

Which precipitated of which metal ions DO. OT dissolve in excess ammonia?

A

Fe2+, Fe3+ and Mn2+

54
Q

What happens when Cu(OH)2 is DISSOLVED in EXCESS AMMONIA?

A

[Cu(NH3)4(H2O)2]2+ complex ion forms

BLUE PRECIPITATE —> DEEP BLUE SOLUTION

55
Q

What happens when Cr(OH)3 DISSOLVES in EXCESS AMMONIA?

A

[Cr(NH3)6]3+

GREEN PRECIPITATE —> PURPLE SOLUTION

56
Q

What is a DISPROPORTIONATION reaction?

A

The dam element has been reduced and oxidised

A-Level Chemistry (12 decks)

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