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Chemistry > Chapter 24 - Transition Elements > Flashcards

Chapter 24 - Transition Elements Flashcards

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1
Q

What are the 2 exceptions in electron configuration of d-block elements?

A

Chromium - 3d5 4s1 is more stable than 3d4 4s2

Copper - 3d10 4s1 is more stable than 3d9 4s2

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2
Q

Define transition elements.

A

D-block elements that can form at least one ion and have a partially filled d-orbital

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3
Q

Which d-block elements are not considered transition elements and why?

A

Scandium - Only forms the ion Sc3+ by loss of two 4s electrons and one 3d electron, causing it to have an empty d-orbital.

Zinc - Only forms Zn2+ ion by losing two 4s electrons, causing it to have a full d-orbital.

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4
Q

What are the properties of transition elements?

A

They form compounds that can have different oxidation states.
They form coloured compounds
Elements and compounds can act as catalysts.

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5
Q

What are the colours of Chromium ions?

A

3+ is green

6+ is orange

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6
Q

What colour are copper ions?

A

2+ is blue

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7
Q

What colour is Potassium Dichromate (VI), K2Cr2O7?

A

Orange

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8
Q

What colour is Cobalt (II) Chloride, CoCl2?

A

Pink-purple

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9
Q

What colour is Nickel (II) Sulphate, NiSO4?

A

Green

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10
Q

What colour is Hydrated Copper (II) Sulphate, CuSO4xH2O?

A

Blue

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11
Q

What are the colours of Iron ions?

A

2+ is pale green

3+ is yellow

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12
Q

What catalyst is used in the Haber process?

A

Iron

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13
Q

What catalyst is used in the Contact process?

A

Vanadium (V) Oxide, V205

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14
Q

What catalyst is used in Hydrogenation?

A

Nickel

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15
Q

What catalyst is used in catalytic decomposition of hydrogen peroxide?

A

Manganese (IV) Oxide, MnO2

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16
Q

Define what a coordinate bond is (Dative covalent bond).

A

A type of covalent bond in which one of the bonded atoms provides both electrons for the shared pair.

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17
Q

Define what a ligand is.

A

A molecule or ion that donates a pair of electrons to a central metal ion to form a dative covalent bond.

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18
Q

Define what a complex ion is.

A

A transition metal ion bonded to ligands by dative covalent bonds.

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19
Q

What is meant by a monodentate ligand?

A

A ligand that only donates one pair of electrons to the central metal ion.

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20
Q

What is meant by a bidentate ligand?

A

A ligand that donates two pairs of electrons to the central metal ion.

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21
Q

Give 5 examples of common monodentate ligands and their charges.

A 
Water, H2O = 0
Ammonia, NH3 = 0
Cyanide, CN = -1
Chloride, Cl = -1
Hydroxide, OH = -1
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22
Q

What is a coordination number?

A

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

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23
Q

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

A

Octahedral

24
Q

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

A

Tetrahedral

Square Planar

25
Q

What bond angle do octahedral shapes have?

A

90 degrees

26
Q

What bond angle do tetrahedral shapes have?

A

109.5 degrees

27
Q

What bond angle do square planar shapes have?

A

90 degrees

28
Q

When is a square planar shape formed in a complex ion? Give 3 examples.

A

When the transition metal has 8 d-electrons in the highest energy d-subshell.
Platinum (II), Pt2+
Palladium (II), Pd2+
Gold (III), Au3+

29
Q

What is stereoisomerism?

A

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

30
Q

What are the 2 types of stereoisomers?

A

Cis-trans isomerism

Optical isomerism

31
Q

When can complex ions show cis-trans isomerism?

A

4- or 6-coordinate complex ions with 2 different monodentate ligands

32
Q

When can complex ions show both types of stereoisomerism?

A

6-coordinate complex ions containing monodentate and bidentate ligands.

33
Q

What is optical isomerism?

A

Molecules are non-superimposable images of each other.

Called enantiomers.

34
Q

Define ligand substitution.

A

One ligand in a complex is replaced by another ligand.

35
Q

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

A

4 of the Waters (H2Os) are replaced by ammonia ligands (NH3), the solution goes from pale blue to dark blue.

36
Q

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

A

The 6 Water (H2O) ligands are replaced by 4 chloride ion (Cl-) ligands. Solution goes from pale blue to yellow.

37
Q

Why does the shape change from octahedral to tetrahedral in ligand substitution of aqueous copper (II) ions with chloride ions?

A

Because chlorine ligands are larger than water ligands, so fewer chloride ligands can fit around the central Cu2+ ion.

38
Q

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

A

The yellow and blue solutions mixing gives a green colour

39
Q

What is formed when Chromium (III) Potassium Sulphate, KCr(SO4)2, is dissolved in water? And what colour is the solution?

A

The complex ion [Cr(H2O)6]3+ is formed, a pale purple solution.

40
Q

What is formed when only Chromium (III) Sulphate is dissolved in water? And what colour is the solution?

A

The complex ion [Cr(H2O)5SO4]+ is formed, a green solution.

41
Q

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

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+.
It is a purple solution.

42
Q

How does ligand substitution help with gas exchange in blood?

A

In haemoglobin, there is a central Fe2+ ion that can bind to oxygen gas.
The oxygen is released into cells and then CO2 can bind to the Fe2+ ion where it is released in the lungs.

43
Q

What is a precipitation reaction?

A

2 aqueous solutions containing ions react together to form an insoluble ionic solid.

44
Q

Describe the precipitation reaction of Cu2+ with NaOH.

A

Blue solution reacts to form a blue precipitate of copper (II) hydroxide, Cu(OH)2

Precipitate is insoluble in excess sodium hydroxide.

45
Q

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

A

The same way that they react with NaOH.

They form hydroxide precipitates that are insoluble in excess ammonia.

46
Q

Describe the precipitation reaction of Fe2+ with NaOH.

A

Pale green solution reacts to form a green precipitate of iron (II) hydroxide, Fe(OH)2

Precipitate is insoluble in excess sodium hydroxide but turns brown in air as it is oxidised to iron (III) hydroxide.

47
Q

Describe the precipitation reaction of Fe3+ with NaOH.

A

Pale yellow solution reacts to form a brown precipitate of iron (III) hydroxide, Fe(OH)3

Precipitate is insoluble in excess sodium hydroxide.

48
Q

Describe the precipitation reaction of Mn2+ with NaOH.

A

Pale pink solution reacts to form a light brown precipitate of manganese (II) hydroxide, Mn(OH)2, which darkens on standing in air.

Precipitate is insoluble in excess sodium hydroxide.

49
Q

Describe the precipitation reaction of Cr3+ with NaOH.

A

Violet solution reacts to form a grey-green precipitate of chromium (III) hydroxide, Cr(OH)3

Precipitate is soluble in excess sodium hydroxide forming a dark green solution.

50
Q

Describe the oxidation reaction of Fe2+ to Fe3+ with MnO4-.

Name the colour of the solution formed.

A

Fe2+ ions are oxidised by MnO4- to Fe3+. MnO4- is reduced to Mn2+.

5Fe2+ + MnO4- + 8H+ —> 5Fe3+ Mn2+ + 4H2O

Solution goes from purple to colourless.

51
Q

Describe the reduction reaction of Fe3+ to Fe2+ with I-.

Name the colour of the solution formed.

A

Fe3+ ions are reduced by I- to Fe2+. I- is oxidised to I2.

2Fe3+ + 2I- —> 2Fe2+ + I2

Solution should go from orange-brown to pale green, but oxidation of iodide is more visible, so solution goes from orange-brown to brown instead.

52
Q

Describe the oxidation reaction of Cr3+ to CrO4 2- with H2O2.

A

Cr3+ ions are oxidised by H2O2 to Cr6+ ions in CrO4 2-.
O is reduced from -1 in H2O2 to -2 in CrO4 2-.

2Cr3+ + 3H2O2 + 10OH- —> 2CrO4 2- + 8H2O

Solution goes from green to orange.

53
Q

Describe the reduction reaction of Cr2O7 2- to Cr3+ with Zinc.
Name the colours of the solutions formed.

A

Cr2O7 2- ions are reduced by Zn to Cr3+. Zn is oxidised to Zn2+.

Cr2O7 2- + 3Zn + 14H+ —> 2Cr3+ + 3Zn2+ + 7H2O

Solution goes from orange to green.

In excess zinc, Cr3+ ions are further reduced to Cr2+ ions.

Zn + 2Cr3+ —> Zn2+ + 2Cr2+

Solution goes from green to pale blue.

54
Q

Describe the disproportionation reaction of Cu+ ions.

A

Cu2O + H2SO4 —> Cu + CuSO4 + H2O

Forms Cu as a brown solid.
Forms CuSO4 as a blue solution.

55
Q

Describe the reduction of Cu2+ to Cu+ with I-.

A

Cu2+ ions are reduced by I- to Cu+. I- is oxidised to I2.

2Cu2+ + 4I- —> 2CuI + I2

Solution goes from pale blue to brown. Forms a white copper iodide precipitate.

Chemistry (20 decks)

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